I dunno if what Thnom suggests is very wise. You might unwrap an area of your model, texture it, then discover later that the way you have unwrapped it means the rest of your layout suffers... what if you need to move, rotate, scale or even re-work the section of UV mapping you've just painted? Then, at best, you'll have to go over the texture and fix any issues arising from this situation...
I think it's a good idea to get a nice solid layout finalised before beginning texture painting. This will also help with consistency, as you can paint any area you choose at a given time, so you can see how different areas contrast against each other.
Basically, get used to using keyboard shortcuts for common functions ... if you're using Max, download Chuggnut's UV Unwrap tools and the UVHelp plugin from www.microcan.nl
... that will sort out a lot of distortion fast and help you get an idea of the best "shape" for a chunk of UV to be in.
Don't be afraid to allow distortion if it means easier texture painting - if you have a curving belt or something on your model, map it as a perfectly straight line, you will get some distortion, but not very noticeable, and it will be a hundred times easier to paint detail into it without having to worry about angle changes.
It's all about practise really... do lots of small, fast lowpoly models and unwrap them, paint them to check how easy the uv-maps are to work with, and ask others for input on what could be improved with each one.
Then try larger more complex models, bigger texture sizes, more complex layouts.
Always bear in mind:
- Simplicity of painting the flat texture.
- You should keep seams to a minimum (ties in with above statement)
- A little distortion is better than a lot of seams (unless you really really need PERFECT square pixels over the model).
- Mirror UV's where you can get away with it - ie. areas that are symmetrically designed, anywhere which isn't really looked at a lot, and so on.
- Asymmetry is more interesting in designs, so don't mirror everything
- Try to re-use texture space, if you want to be really conservative. Certain areas of armour, skin, cloth can have the same texture, even if they're on totally different parts of the body or object. As long as the shading and colours match up, it's fine. Gives you more pixel space to play with.
Ehh, I think I talk too much.