There's a lot of miniature gaming sites for for example Games Workshop's games, that can give You excellent painting tips.
I've painted a lot of Warhammer and 40k armies, I'm more of an 'army painter' than a maker of center pieces. I have usually got good points for painting in tournaments.
The key thing in painting miniatures is to utilize the models three dimensions. You are not painting porcelain or on a canvas. So, the miniature is small, but the sculptor has already put in the details. These FFG's models aren't nowhere near the quality of 'real' miniatures from GW, Racham, etc, but good enough for a nice result. There are different simple methods to get a reasonably good results in a limited time. I spray the models first with a white spray. Then when painting, I use very dark and highly diluted paint with water. The effect when painted on three dimensional, white figure, is that the thin color makes the recesses seem dark and the raised details light, for example in a cape or chainmail. When painting a red cape, I use red, tint it with black, then add lot of water. There are specialized miniature paints from Citadel (GW) and Vallejo that You should use.
The brush doesn't need to be thin, the precision is not really an issue. When the colors have dried, You can then highlight parts by drybrushing (very dry brush, light color, the color touches only the raised details), add washes (darker, even thinner color) to emphasize the recesses etc. I usually paint for example the skin first on darker tones, and the use lighter colors as 'make-up'. Citadel even produces really good ready-made washes that are just fantastic.
Of course there are many techniques in miniature painting, but painting good lookin miniatures is more about having eye for colors than having a really steady hand and a thin brush.
And, a painted miniature looks so much better than grey plastic, even if it is Your first work. Just give it a go !