How to find major customers of particular worldwide public company (Introductions)?

If I go by your definition, I am getting the notion that by particular worldwide company you are referring to an MNC. You must understand few important things when it comes to MNC:
A MNC is a company that does business in more than one country. Transnational company produces, markets, invests and operates across the world. It is an integrated global enterprise that links global resources with global markets at profit. These companies have sales offices / manufacturing locations in many countries.
a) MNCs consider opportunities globally
b) MNCs invest their assets globally
c) MNCs engage in international production
d) Operations in number of countries
e) Managerial decisions based on global perspective.
f) MNCs produce the products in one or few countries and sell them in most countries. Transnational corporations produce the products in each country based on specific needs of customers of that country and market these. A transnational corporation mostly uses the inputs of the host country where it operates unlike an MNC.
Companies become MNC because of several reasons for instance:
i. Protection from uncertainties of business cycles, political policies of the domestic country
ii. Tap global markets
iii. Grow business
iv. Increase profits
v. Reduce costs
vi. Overcome tariffs – In some countries, the companies need not pay tariffs, if they manufacture in that country and export those goods. So, such companies set up manufacturing facilities in those countries. E.g. NAFTA countries like USA, Canada, Mexico (NAFTA – North American Free Trade Agreement).
vii. For technological advantage – instead of licensing, companies produce goods directly
Advantages of MNC are as follows:
i. Contributes to economic and industrial growth,
ii. employment generation,
iii. access to latest technology,
iv. more business for domestic suppliers,
v. more competition for domestic business,
vi. reduction of imports,
vii. favourable effect on balance of payments,
viii. domestic consumers get plethora of products and services.
ix. MNCs who export also earn foreign exchange.
x. Good utilization of natural resources.
Drawbacks of MNC are as follows:
i. Unsuitability of technology to host country,
ii. MNCs may not operate within the boundaries of national sovereignty,
iii. they may indulge in monopolistic practices,
iv. indiscriminate use of natural resources,
v. focus only on consumer goods but not capital goods or development of infrastructure in host country,
vi. pollution, dumping of material,
vii. use of outdated technology to host country.

Advantages of MNC to home country are as follows:
i. Create demand for home country products,
ii. create employment for home country people,
iii. earn forex for home country, produce products required by home country consumers by producing in foreign countries with foreign resources,
iv. save domestic country from environmental pollution,
v. generates profits for home country by earning profits through business operations in host countries.
Disadvantages of MNC to home country are as follows:
i. Transfer capital to other countries, unfavourable balance of payments
ii. Less employment opportunities in home
iii. May neglect industrial development in home country as transnational companies follow secular approach
Characteristics of an ideal MNC:
a) Lose its parent identity and blend in where it operates
b) Citizen of the world (absence of a polycentric approach)
c) Takes up CSR (Corporate Social Responsibility) efforts
d) Meet customer requirements across the world
e) Seek efficiencies
f) Seek new technology and new knowledge
g) Act within the framework of local law, rules and regulations

The ideal MNC transcends the national boundaries and detaches itself from narrow national considerations. Therefore some people refer to MNCs as transnational corporations. A transnational corporation is globally integrated i.e. its considerations are for the entire worldwide operations as a whole; but at the same time, it respects the local (national) requirements.
Multinational companies with total control from home country or companies with decentralized operations in different countries move towards becoming a transnational corporation. Global companies with a firm base in the home country and tight control over foreign operations also move towards becoming a transnational corporation.
Developing countries should note that the size of a country’s domestic market may not be a limiting factor in the establishment of successful MNCs abroad. Small countries like Switzerland and Finland have spawned MNCs like Nestle, ABB and Wartsila. The growth of businesses need not follow a linear path. Companies can take the international route and scale up their business.
Off shoring is shifting an activity abroad. R&D can be outsourced but there is a risk of losing protection offered by intellectual property rights. Back office processes, technical support functions like data entry, data processing, secretarial services, telemarketing, legal transcription and business process outsourcing are services that are generally subject to off shoring.
Data processing, database services, software implementation, financial services, animation services and health services are also subject to off shoring. Medical transcription, diagnostics, testing and medical advisory services can be outsourced outside domestic country.
Now once you have understood this, you will also understand the fact that most of the companies which operate worldwide do have a strong social networking base as well i.e. social media to make it’s presence felt in the business market.
The reality of individuals getting intricately connected with each other through the social media (as seen above) cannot be ignored by any business, whether it is a large corporation or an SME. Customer has always been a king and businesses are constantly trying to reach out and seek attention of their consumers for new leads, feedback, research, and service. Ever since social media has become the new destination for millions of people, it is the perfect platform for businesses to carry out or support some of their business functions online. Today, more than 90 percent of the adult online population is using social media, which includes many of your customers who are networking with others. No business can ignore social media anymore. If you are, you are not only losing an opportunity to enhance your business, but your absence may also be causing damage to your brand and reputation. Social influence has always played a major role in the buying decisions of customers. But now more and more people are relying on the social media online to seek referrals and recommendations from others, asking / answering questions and sharing their experiences. It is not only the big multi-national or national brands, the phenomenon can be seen taking place at the local level; theatres, restaurants, etc, are all being discussed on the social media. Businesses usually refer to the social media as a consumer-generated media (CGM). Social media can be differentiated from industrial or traditional media like magazines, newspapers, television, and film, as they are relatively inexpensive, easily accessible and enable anyone (private individuals) to publish or access information.
Benefits of social media to businesses are as follows:
a) Accessibility: The social media is easily accessible and takes minimal or no costs to use. Social media is easy to use and does not require any special skills, knowledge to use. It is absolutely simple to connect with others and be a part of communities. Therefore, anyone with online access can use the Social Media to initiate or participate in the conversations. In a sense, everyone is now empowered to speak up.
b) Speed: The content that you create on the social media is available to everyone in your network/forum/community as soon as you publish it. You can communicate with your audience without any external factor affecting the delivery of your message. The responses are also near instantaneous and thus you can have a dialogue, which is almost in real-time.
c) Interactivity: Social media affords a two way or multiple communication channels. Users can interact with each other; ask questions, discuss products/services, share opinions and anything else they might be interested in doing.
d) Longevity/volatility: Social media content remains accessible for a long time, maybe forever, because of the nature of the medium. In addition to this the content can be edited/updated anytime. So, if a user likes a particular product and says so in the social media, it is not a permanent positive vote for the product; the user can always go back and change his opinion anytime.
e) Reach: The Internet offers an unlimited reach to all content available. Anyone can access it from anywhere and anyone can reach, potentially, everyone. Social media offers the same facility to all the users who can share anything with anyone they like.
f) Online Branding: Every business wants to be known as a brand, which is, in effect, its “identity” that may be represented by a name, logo, colour schemes or the tag line. But, the term “branding” goes much beyond just these and is in fact a culmination of the individual “identity” of the business, how it differs from its competitors and why a buyer should come to it.
g) Marketing: Social Media Marketing is the way businesses and non-profit organisations use the social media effectively to build relationships through trust, useful content, helpfulness, and authority.
h) Building Relationships: For a business to be successful it needs satisfied customers, and for a customer to be satisfied they need good customer care and service. A satisfied customer is a loyal customer. So how can a business provide good customer service, care, or support?
i) Word-of Mouth / Networking: Social Media is the new Word-of-Mouth. Since people are all inter-connected with each other, a small mention in any of your audience’s profile goes a long way in spreading the word about your business/product. Let your customers become your marketing agents.
j) Online Reputation Management: “The practice of monitoring the Internet reputation of a person, brand or business, with the goal of suppressing negative mentions entirely or pushing them lower on search engine results pages to decrease their visibility is known as online reputation management (ORM).”
k) Community Building: A company or business can use the social media to build a community around its products/business. Vibrant communities create loyalty and encourage discussions, which can contribute towards business development and improvement.
l) Lending a Human Face to the Business: More and more customers are sick of the marketing jargon and are not comfortable dealing with faceless businesses. People like to deal with people and participation in social media helps to lend a face to your business.

Thus, the answer to your question is that to find major customers of particular worldwide public company tap into the social media influence of that company. You will not only get customers there but also ex-employees who will help you know understand the company well. Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath

I have an idea that you might consider. While there are different ways to make introductions, and i'm sure you have already tried LinkedIN and other lead generation programs that can help you by targeting companies? But if you are targeting law firms, often law firms need to bring in presenters for continuing education. If you have something to offer that could be considered for education, you might use this as a way to make a connection with the law firms - once they know you, they may be more open to partnering with you in order to introduce you.
-JL