I always get 0 for percentage when I do this:
int trackBarValue = trackBar.Value;
float percentage = trackBarValue / 100;
What's wrong with my code?
The problem is you're doing an integer division, which is truncated. Try this:
int trackBarValue = trackBar.Value;
float percentage = trackBarValue / 100.0;
This will do a floating point division, and given you the result you want.