- Do you paint before you Assemble the model (each piece seperate), before gluing to the base, or after you glue to the base?
This is mostly a matter of personal preference and practicality. I'm of the mind that if I have a really hard time accessing a particular spot with a paint brush, I probably will also have a really hard time seeing that spot when all is said and done. I also prefer to have models on the table, ready for action, and paint them as I go. With only a few exceptions, I assemble and attach to the base before priming/painting. Some odd parts might get done separately, like shields/wings/capes that will block application of primer/paint to otherwise visible sections.
- Is using a primer necessary or can you just do a base coat of whatever color you want?
Primer is absolutely necessary. If you're using acrylic paints (recommended) then you'll need primer for the paint to adhere properly to the model. Painting directly onto pewter or plastic will result in your paint chipping/peeling almost immediately. Primer gives the paint a proper surface to 'grip' onto, and also helps to fill in some very minor imperfections in the model's detail.
2a. Which is generally better to use in regards to primers? White or Black?
Again, this is one of those decisions that's part preference and part practicality. Generally speaking you want to pick a primer color/tone that matches the overall color of the area you're going to be priming. Since nobody primes their model in 17 different colors, though, the decision will typically come down to "What color is this model mostly going to be" or "Is this model going to be mostly light or dark". If you want to paint a lot of white, yellow, tan, and so forth, prime in white or light grey. If you want to paint a lot of black, blue, green, and so forth, prime in dark grey or black. If in doubt, prime in grey and go from there. With enough layers, any base coat will sufficiently obscure the primer so it won't make as much of a difference. Personally, even though I paint most of my models in light colors (Legion studio scheme), I've taken to priming with dark grey and black. It helps me make sure that I'm actually base coating evenly (as opposed to painting white on white), and any small spots that I do miss tend to be in small crevices and recesses, to they end up looking like dark shadows, which is perfect.
- General Tips/Tricks/Advice?
There are tons of articles, videos and guides out there showcasing everything from basic tools and techniques to advanced blending methods involving the use of 3 brushes, exotic mixing media, and synchronizing your painting schedule to the winter solstice. But once you've got the basics down, nothing beats plain ol' practice.
Don't be afraid to put paint on a model. Even if it looks like crap, hopefully you'll learn something. Take that to heart, and continue painting other models. Don't repaint your first models until you've gotten a few dozen under your belt, that way you can have a showcase of your progression over time, even if only for your own edification.
Oh, and thin your paints. Seriously.