Anyone have any experience with licensing/selling the rights to software they've written?

I have two scenarios developing for my business as follows:

Company A may be interested in reselling my product to their customers.  Not a typical reseller though as they would want to integrate my product into their business and use it as a tool to give them a competitive advantage over other companies in their geographic location.  Company A is not a software company.

Company B is a software company.  They may be interested in either reselling my product or integrating it into their suite of products.  I'm assuming if they wanted to integrate it that I would have to sign over exclusive rights and give access to sourcecode for X number of years or something.

I'm really just looking for comments from people who have been in this situation before, what I should expect from each company in each scenario.  Basically what I should be sure to do so as not to get ripped off since I'm new to the negotiation process! =)