I'm sorry to tell you, but we can't help.
The problem is that there are so many things that could be slowing down your software, that to give you any concrete results, we would have to give you such a massive list of generalities that you would have to wade through it for hours looking for anything that might be relevant.
So, instead, here is what I do when I need to speed up software:
1) Quantify the problem. Add code to measure the actual speed, and record details for what parts of the software are performing quickly and slowly. This gives you numbers to check your "improvements" against.
2) Target slow features that are commonly used. Ignore those that aren't done often - they can be worruied about later if they are a problem.
3) Add timing until you get a sense of where code is slow: it might be in your DB access, or it could be that you are transferrign large amounts of data that you don't use.
When you can tell what is slow, you can start to look at (or ask about) improving that code.
For timing, look at the
Stopwatch class.[
^]