E.B.
We also painted our old ugly cupboards and the end result was great. We cleaned the cupboards with TSP, which is a cleaner they sell at Home Depot, Lowes, etc. You should clean them before painting. Even if they appear clean, there may be years of grime or oils from cooking etc, that you can't see.
One thing I would suggest: clean, paint and stain one relatively small area, and let it dry and look at it from different angles, in different lights (morning, evening, with day light, with the electric lights on, etc). I was so surprised after I had cleaned and primed the cupboards that the color I then began painting was not coming out to be the color that I had chosen. I didn't understand why it looked so different, so I went back to the paint store for advice. They explained that, with wood (and the stains) paint colors may appear different, and thankfully, the solution was as simple as choosing a different primer. (I hadn't consulted them, I just bought a standard primer without any advice). They took back the regular primer I had bought and exchanged it for a gray-based tinted primer. That seemed weird, and it looked kind of gray (which was NOT the color I had chosen), but then when I put the paint on, it was the perfect color that I had intended it to be. So tell the paint store tech what your cupboards look like now (bring a photo) and review the color you've chosen and ask if a certain tint of primer would be best to achieve the proper result.