My three best recommendations would be Testors Model Masters Acrylics (not the enamel crap they sell, though!), Citadel brand paints from Games Workshop and Tamiya Acrylics.
That's just for figures, though. I haven't tried my hand at customizing vehicles yet.

The only advise that I can give is don't spray-paint the rubber parts of vehicles or the "bendy" parts of the figures. I always found that the cheap "Apple Barrel" brand paints work just fine from Wal-Mart or any store that sells cafts.:)

I use a combination of Model Masters Acryl and Appel Barrel for both vehicles and figures. Spray paint works great for vehicles as well, but you may need to sand them or use a primer depending on the surface.

Also if you're repainting newer figures it's important to wash them thoroughly with warm water and dish soap (anything with citric acid in it). This will get rid of the mold release agent that can keep paint from adhering well to plastics.

Greetings...

Greetings! Welcome aboard.

--Death

we certainly are! Welcome

Paints? Well, I'm in the minority here because I use enamels only, no wishy washy acrylics for me. For both figures and vehicles I use Humbrol or Revell semi matt enamels; they're tough, they come in a great range of military colours, and the semi matt finish matches the factory paint finish perfectly. On larger vehicles I also use matt enamel spray paints for a better finish than brushing.

I paint my Marauderinc weapons with Tamiya colors.

I've never used enamels, but if any one goes with acrylic, Games Workshop is the way to go.