1) The very first thing you need to do is keep working like the aquisition is not going to happen because these things more often fall apart than go through and it can really screw up your start-up if you start planning for it going through.

2) Next, you need to decide if you want to stop working on your own thing and start working for someone else and figure out the minimum price you would do that for. If you would accept one dollar less that is not a minimum price.

3) Next, you need to find out if this company will meet that price.

4) If they will meet that price, only then should you get a lawyer.

Getting a lawyer as a first step is terrible advice that will cost you a lot of money and a lot of time on something that 1) you many not be interested in 2) may not actually happen.

We were in a similar situation a month ago and this was basically the advice we compiled from angels, people at YC and pervious YC companies that were bought.

We ended up mostly ignoring the acquisition talks because we weren't that interested in being acquired and (as people told us would likely be the case) they did not go through. It would have been a huge waste of time and money if we got a lawyer like some people on HN suggested, before actually figuring out steps 1-3.