Since you have not mentioned whether this is an actual product or a service, I will try to cover your question a bit more generally.
1. Find mid-level contacts in the targeted enterprises for specific areas that might deal with your product/service and start talking and building relationships with them. Ideally but not absolutely necessary try to get introduced through a connection - you will get airtime more easily. Figure out who would make the best influencer/evangelist internally for your product/service. You WILL need a champion from the inside.
2. Think of your product/service from THEIR POINT OF VIEW: can they gain added value from their current products/ services by introducing your product/service - it's not always about revenue share for a service for example. Most enterprises have a strategy that focuses on their CORE offering so any additions have to dovetail well with that.
3. Present the product and ask LOTS of questions on whether they have a strategy/roadmap/planning/roll-out to cover the customer gap your product/service will be filling. If not, ask for pain points/problems/issues that are at the forefront that might support the need for your product/service.
4. If your product requires integration, find out their budget cycle and roll-outs planning to see where you fit in (ideally you should be integrated in next year's planning). This is how most products miss the boat - they are not on the priority list and are more likely to drop off as the year end budget pressures come in.
5. Think, plan in advance and present how you would cover a large enterprise deployment (depending on your product/service): can you scale the product/service for large number of users, do you have the resources to support enterprise grade SLAs including but not limited to customer support, training, sales, maintenance, response timeframes, deployment timeframes, disaster recovery, financial/regulatory etc - all depending on what kind of product or service you have.
6. Ask what their supplier approval processes are. You might need to go through a qualification process and you will need to fulfil certain parameters to qualify (such as maintaing a certain level of insurance for example).
A some food for thought: a lot of large enterprise decision makers tend to focus (unfortunately) on the short term impact (3 months to 3 year horizon), as this is how they are evaluated and their targets/incentives are set. Can your product make a difference to their revenue in that timeframe?
Happy to answer more specific follow-up questions.