I am going to put the wisdom I have gleaned from my experiences painting minatures here. These tips are just that, tips, so you might have painting strategies that work better for you. So be it.
Use Citadel paints and brushes on your minatures. Though pricey, their quality is unmatched. If you are really strapped for cash, you could buy another company's paints. Even if that is the case, you should still use Citadel brushes and washes. They are the best. As far as I know, Citadel is the only company that produces high quality spray paints for use on minatures, so use those too.
Terrain is another matter. You would have to be insane or a millionare to use those costly Citadel paints and brushes for massed areas of terrain. Tempra paints work just fine on most terrain features, but you should be sure to give them a good coat of varnish. Cheap brushes are fine for most terrain.