Often the expectations of the founders and corporate development people are very divergent. Before proceeding far into conversations with big acquirers, you should try to clarify valuation expectations (and other important consideration details, like retention packages) as quickly as possible. This strategy should help prevent you from having half a dozen meetings, only to find out the potential acquirer expects to pay $10 million for your rapidly growing startup that already has a term sheet for a $15 million A round.
When you have an offer, the next thing to do is determine your alternative options. You can do this by letting other potential acquirers (including larger companies you have partnered with and/or competitors to the acquirer) know that you have received a term sheet from an acquirer and you are considering selling yourself, but would prefer a longer term future with their company (find a reason). Now would also be a good time to call up VCs you have been talking to and ask for a term sheet for …
… can work together. These conversations usually involve many different people within a big company; you’ll only get an offer once a sufficiently high-up decision maker is convinced that buying you is a better idea than partnering with you.