The biggest challenge, in my experience, will simply be to break through the pre-conceived notions of domestic clients, and give them some confidence that your service can actually do the job.
Americans in particular have a hard time going offshore because there are so many disaster stories and many clients have already been burned before. Unfortunately, the belief that offshore development 'doesn't work' is not completely unfounded - a high percentage of projects fail. Even domestic projects are plagued with schedule and budget issues, and going offshore just makes this harder. So, we have our work cut out for us when we are trying to convince clients to consider overseas developers. This is especially true in India, which nowadays has about the worst reputation in the offshoring world except perhaps China.
That said, there are tons of companies that are doing great and are able to attract overseas clients and grow quickly. To do this, you need to have a real differentiator, and a real way of breaking through the skepticism that you will face. It's absolutely not enough to say that you can provide a PM, that you are ISO certified, or any of those types of claims - all shops say that and it doesn't mean much (most PM's are terrible anyways).
Figure out what your company can offer that will give clients a real feeling of confidence. In most cases, this is not going to be a bunch of case studies or claims about vague processes - it will be in the area of communication skills and professionalism.
There is no single greater fear in the minds of potential offshore clients than the fear that the communications will be excruciating and will derail the project. In my company, we try to get clients right on the phone, to demonstrate that we can assign a fluent/native English speaking project manager who will be with the client from beginning to end. Then we try to make contact with one of our developer leads, so that they can see that there is a real human who communicates well and will collaborate with them on their project.
This works wonders. Imagine how it would feel to have someone speak to you in perfect English, then say "Don't worry, we'll assign a great project manager to handle your project once you get ready to start" - that leaves a lot to the imagination. Better to prove that you have those skills right out of the gate.
Generally, the teams that are most successful don't spend a lot of time pitching clients on their technical skills or their processes, or even their former clients. It's the teams that make immediate, intimate, productive, constructive contact with the clients and demonstrate great communication skills and organization - that is what gets clients attention.
In my business I usually place clients with offshore teams, but I also consult to offshore teams about how to get clients (or how to go agile). You would be amazed at the feedback I get from both vendors and clients. Clients say they are deluged with offshore teams constantly sending them the same, tired sales pitches. Vendors say they are trying to develop leads, but the prospects usually ignore them.
If you want to make sales, consider building confidence with potential clients by showing them the individual people that they will be working with, so that they can see (and hear) for themselves what it's like to collaborate with those people. Or, just find the one differentiator that you have that will build trust and confidence, and promote that instead of doing the 'same old pitch' that all the other teams do.
Also, be prepared to speak very frankly about the issues associated with india, and how you plan to overcome them. Be sure to have a strong answer about how you will deal with attrition and culture as they pertain to offshore development in India - every savvy client will want to hear this.
Good luck !!