If we are talking anything 7-figures or above...find an investment bank/broker.

Sure you'll end up paying them a hefty cut...but you won't get screwed.

Plus, if you're getting interest from one large company, there are probably others interested as well and a good broker can run an auction for you to get a much better deal than trying to do it alone.

Selling your company isn't something you should do by yourself in my experience.