I work for a small-to-mid-sized (~20 employees) tech startup in Europe. I was hired two years ago as one of the first employees after the founders. When I joined, we had an agreement that after a certain amount of time, and when certain business criteria are met, I will be offered a raise and a percentage of equity. Well, time for negotiations have come and I really have no idea of how to evaluate such offers. My current salary is OK, but based on my rather specific skill set I know I could earn more somewhere else. Also, while I know that I can be replaced, I am currently in a key position for the company's products, and I think they would have a hard time finding someone quickly, and would have to pay this person definitely more than they pay me now. They will come up with some numbers soon, and I have not the slightest idea of how I evaluate, lets say a raise of X plus Y percent of some sort of shares. While I can tell if business is going well or not due to the number of projects n my desk, I have not the slightest information about the company's finances, and I don't think that they will let me check the books (and even then I wouldn't really know what to look for).
What do I do here? Apart from my personal situation, how do I decide if the offer is good or not?
If it helps, the company is based in Asia, but I work in Europe and under European law.