Few very general tips.
a) the AGEOD system often rewards doing nothing. If you can't see a good reason to move a unit, then don't - as above let it sit and regain cohesion etc;
b) keep a close eye on supply. Check over the wagons in a stack - are they red (empty), keep an eye on the supply indicator on the right hand of the stack screen (at the bottom), are you running short? Send wagons back to a supply source to refill (and escort them);
c) in the main, don't march in winter, you pick up a lot of cohesion loss (so your units don't really fight) and run out of supply. Supply wagons act as a buffer against extra attrition but equally are emptied out much quicker;
d) keep a close eye on the command points (CP) used and needed by a stack. As far as possible try to avoid any malus here, certainly try to keep the malus under 5% (if you don't again your units won't fight very well);
e) leadership traits really matter (sometimes more than the raw scores). Need to move quickly - do you have someone with the fast mover trait? Need to operate in a region with poor supply - do you have someone with the traits that help here?
f) also about leadership note that some traits only come into play if the commander is in charge of the stack, others if they are present in the stack;
g) stances split into two groups and its worth thinking about what you want to do:
g1) green-green is great for 3 things. You recover cohesion very quickly (and limit cohesion loss if you move), you will fall back out of combat very quickly (assuming this is what you want to do) and its good for scouting forces - especially if used with the 'evade combat' option;
g2) defend is the default stance if your leader is inactive (but you don't take control over a province), attack is needed if you will attack (but you don't gain any defensive terrain modifiers), assault is only needed if you plan to storm a fortress;
g3) commitment levels, well green as above means you will abandon a battle quickly, blue/orange are the default options and red means you won't retreat (be careful as you can get very badly beaten using this);
g4) combinations assault-orange means you will assault any city you end the turn in the province with, assault-red means you will assault cities as you move (can be good to capture a chain of weakly held cities);
h) going back to supply, a province will generate supply in its own province and send this to armies in adjacent provinces - any further and you need to use your supply wagons to move it;
i) the combat power measure is useful but limited. Some leader traits allow units to fight better/worse. Some units are better in certain terrain than others, some are better on the defense and so on. Also combat power degrades quickly as you lose cohesion, so if you force your units to march across poor terrain with limited supply then even the best army will not fight very well. So combat power can change as the turn develops;
j) frontage matters as well, a huge stack can only deploy some of its strength (this may be good = reserves) but it does mean that defending in poor terrain can bring the largest army to a halt (it can't fully deploy);
k) there are some posts in the Wars of Napoleon section that may help. You can ignore the stuff on march to the sound of the guns as that doesn't apply here but some of the other discussions about frontage, stack and unit selection for combat may help once you have a feel for the basics;
l) Military Control (MC) is an odd concept. Basically it indicates how much you dominate a province but the consequences can be important. If you move into a province where you have low (or no) MC any stack will be changed from defend to attack stance. You might want this (it means an 'inactive' general might attack - at a malus) or not, but it can cause confusion if you aren't expecting it. Sometimes opposing armies can be in the same region (esp if both are now on the defense - by choice or due to leadership problems), this can create problems for resupply and the movement of extra forces in and out;
We can always count on loki100 to help the guys new to, and even the not so new, to Ageod games.