If you've been in a sector for 10 years, I imagine you know who within that sector has money to spend. There's no point in going after a segment without money, right?

Once the segment has been identified, I'd then think about the sales process-- how well are you poised to sell to the decision-makers in this segment? Keep adjusting until you have a good fit.

Then, you turn to the final piece of the puzzle: what do you need to do to get these people to put their money in your pocket? What products or services do you need to provide? Generally, this means looking at a problem they have that is currently underserved; not necessarily a problem that no one else is attempting to solve, mind you, but one where you see an opportunity for competition or disruption. Sometimes, this means solving a problem they don't know they have-- if you can find some way to cut their costs or increase their revenue that they haven't thought of, for example.

When in doubt, look inside their organizations for critical processes that are still being done by Excel spreadsheets, and build a better alternative to these.