Hi N00B painter here. I saved the best advice for last. ^_^
- Always thin your paint before application. All that's necessary is a few drops of water from your brush. Thin paint on your palette only. Do NOT thin in the paint bottle! Don't use anything other than water for thinner starting out.
- There are many step-by-step mini painting videos on YouTube. Some are good; some are bad. Take the advice you like and experiment with it. I haven't tried the more high-end paint tutorial DVDs yet. =\
- Get a book on "How To Paint Citadel Miniatures." They really do help.
- The new Citadel shades make painting WAY easier than it used to be.
- The best advice I can give is to make your first thousand mistakes up front and learn from them as fast as you can. And the cheapest way to do this is to buy a few bottles of Dawn Power Dissolver.
It's a foam spray cleaner/degreaser that strips paint without harming metal or plastic. Just put badly painted minis in a container and soak them down; then leave 'em overnight. Comes right off with a toothbrush!
So now you can practice on one mini until you can get your technique down, or until it looks just right.