[MajorDisaster]

A lot of useful tips on this thread. I've not played a game like this for a while & there's plenty to learn :-) Agreed the AI has this knack of parking units in frustrating places, but on the otherhand Ive seen it do some really stupid stuff too - just like real people :-)
I think the keys are not sticking your neck out too much & too often and a balanced force, in terms of quantity and quality. Have a little bit of everything. Going for lots of Cheap can end up in massed routs. If you have All Expensive then you dont have the numbers to cover the ground and every casualty hurts the points bank. (Some throw away infantry in your core is useful - after all, if they survive they gain experience so you cant lose).
And my biggest screw ups have been allowing my tanks and infantry to get seperated. A big No-No.

Hveldenz says it exactly right. On attack/meeting missions Ive done about the same as him.. err.... so far.
Choose carefully what you think is the best place to attack, and do so with the bulk of your armour & inf, but make sure you have your flanks covered (AT /TD's /HMG's /Flak).
I notice the AI likes sending T34 spoiling attacks along the very top and lower edges of the map even when it's on a delay mission, so make sure even extremeties are covered by recon. (h/track aufklr great. ditto a m/cycle zug).
I also tend not to occupy the 1st victory hexes with the lead unit. Get a decent sized force (Armour platoon plus infantry) to the locality b4 "stepping onto" the hex. That way you'll be ready for a likely inevitable AI counter attack. Even better if you can motor in some AT too.
Oh yeah, and of course, know when to runawaaaaaaaaay,,,