The Holy Grail topic for figure painters... how to base, what to paint it, how much grass etc to stick on.
Here is my tuppence worth for what it's worth:
Use thicker rather than thinner basing material - if you put lots of - stuff on top it can warp and curl up at the edges.
Use a craft knife to score across the bottom of the base in a cross hatch pattern ensuring the cuts leave the edges - this allows the stresses from warping to 'run out' and not be caught in the mass of the base causing warping.
Undercoat in a dark chocolate or similar.
Use 2 lighter dry brush layers could be anything from flat earth to khaki.
Never finish anything in pure white highlights - I generally avoid pure white even on uniforms making my final highlight 'off white' or very pale sand. I also try and avoid pure black where at all possible.
Put a shadow round the feet of the models by running a medium to dark brown wash in there.
Create ground variation by washing areas of stones or rough sand in a watery wash of mid/red/dark brown.
When you put static grass on top I always dry brush it - Japanese Uniform is a great shade for burnt grass. Static grass from a packet often has a glossy sheen to it and catches the light. The dry brushing not only fixes it down but reduces the sheen.
Use a few tuft and plants but not too much. I used to use flowers but tend not to do that now as I think they make the soldiers look to 'happy'
I always paint the edge of the bases too - usually brown violet or olive drab. I like the neatness.
two pennies now up!