As I think of them, I'll add them to the list. In no particular order.

Use good quality brushes. Get yourself some Kolinsky Sable brushes - I use Windsor & Newton Series 7 Rounds. Crap brushes will get you crap results, so it's totally worth shelling out a few extra bucks for the top of the line.

Vallejo Model Colour reds cover very well, even over black, in a single coat. I suggest using 859 Black Red (035) or 985 Hull Red (146) as a base color.

My favorite dark brown is VMC 822 German Camo Black Brown (150).

Never add black to a color to darken it. It will become muddy, flat, and lifeless. Instead, add either dark blue, dark purple, or dark brown - or add the color's color wheel opposite to it.

Never add white to a color to lighten it. It will become chalky and pastel. Instead, choose an off-white or bone color, or simply a lighter shade of the color. Or add yellow - after all the sun is what makes things lighter.

Don't try to force paints to cover in a single coat. Have the patience to apply several smooth coats if the color doesn't cover right away. Trying to force it will result in a clumpy, gloopy mess. That's right, I said "gloopy."

Use separate rinse water containers for regular and metallic paints. This way, you avoid getting little metallic flakes in the rest of your paints.

Use heavy rinse water containers - I use Mason Jars - so that a little errant bump won't send dirty paint water all over your desk and whatnot, like can happen with plastic cups.

If you ask someone what colors they used to paint something, and they tell you, don't then ask them what that recipe would be in a different brand-name of paints. That's what they used, so if you want to emulate it, then go buy those paints. Paint Lines are not equivalent to each other, which is why a lot of painters use paints from many different companies.