drill small holes in the wheels where they will contact the ground, isert a piece of wire and use these to tack it to the base.
I also use very thin and long woodscrews and drill a hole in the bottom of the hull of the vehicle close to the tracks. The screw is inserted through this and into the base. Then I pop the turret back on and it is pretty secure.
Couple of holes drilled through the groundwork and the base about 1/4 inch apart and fishing line is run up through the base, tracks and back down through the base and sinched tight.
Glue.
When I make my groundwork I set the vehicle in to make an appropriate depression. Once dry it now has a pre formed "socket" to fit in and I take a weight and put it in the vehicle to make it seat. Turret goes on and it looks fine.
It really depends on the vehicle, the end use of the base (if the vehicle is going to be changed out) as temporary display base for shows, or if its going to be part of a diorama where the ground material can cover any mechanical attachments, or if the glue is sufficient to leave it stand alone. If you forsee wanting to change out your model or make it so it can be reworked or added to another diorama then temporary soluitons are the thing.
Mike
"Imagination is the dye that colors our lives"
Marcus Aurellius
A good friend will come and bail you out of jail...but, a true friend will be sitting next to you saying, "Damn...that was fun!"