Well first off, you should pick your fights, especially when starting up. And of course you should level up on leader skills like surgery, leadership, and tactics, and keep morale in check. I may be biased in this as a cavalryman but I think being mounted yourself will help lead as you can move across the field faster and also thwart cavalry if need be, not to mention hit-and-run, at the least. You should also organize the party list in a smart way for when you're constrained to fewer units yourself because of higher enemy tactics. Placing higher tier first helps, but don't leave the weakest for last (this may vary though).
An obvious thing is to take advantage of terrain. For instance place your archers high and spread out between trees, especially if the enemy has cavalry. If you're up against a big cavalry, put all your units on the summit of the highest closest hill and try to divert the cavalry yourself (well, better have riding skills and do maneuvers). I almost always order infantry close together and may put them near archers if there is enemy cavalry. Also, as a slight "hack", you should back up your troops to the map edge to stop cavalry, with a wall of infantry in front, but close.
I found the cavalry to be kind of dim most times. If ordered to charge they will of course do just that and clash, most often becoming stuck between enemies. I either make them follow me and do sweeps of the enemy, or make them wait on some flank, preferably not very exposed and order them in once the enemy gets disorganized, if there's no enemy cavalry. If there is, it's cav vs cav.
If your party is mostly made up of recruits you can babysit them if you say you can handle it by yourself. Just make them keep position in a good place and try to do as much damage as possible by yourself, maybe leaving the weaker enemies alone. They will get some experience. Another thing I found works for me with infantry is to place recruits after elites in the party order list. That way it seems the recruits advance a bit faster since they're near the heat. Now I mainly played with Nord units but it should be generally viable.
As for tactics you really should try to be explicit with them. Sometimes I forget to order the infantry to advance so what happens is that they'd just stand while taking ranged hits. Or maybe you might want archers to hold fire until the enemy is in good range. I'm not sure of the threshold distance, but archers will start holding fire if your own infantry is in the way, so you might want to delay the infantry until your archers have their fun. You should also look at typical behavior of different factions and see what works. I also only use only a few of the available orders, since they seem to suffice, so I've memorized the hotkeys for quick ordering.
Of course, be very careful with assessing enemy strength and with timing. When you've got mostly recruits, wait until you have superiority in numbers before sending them in, especially with infantry, because when they meet it will just be good unit beats weak unit, then moves to next weak one and maybe gets a few hits in. Also you should keep in mind some paper-rock-scissor rules, as not sending cavalry against pikemen or light armored and/or unshielded infantry against a nest of crossbowmen (unless you've got elite troops and the enemy has weaker units). In armies, the AI will place elite units like sergeants and marksmen among weaker units. Those should be your job if you have lower tier troops.
That's all I could think of at this hour. Be creative but treat you troops with care.