My armies tends to be rather cavalry, than infantry based..

4-6 units of heavy cav(Knights of any type that are available at the moment)
2-4 units of light melee cav(hobilars, mounted sergeant, steppe cav, whatever is available at the moment)
4-6 units of shooty cav(mainly mounted crossbows, jinetes, heavy steppe...few catholic factions cant have shooty cav, so i pick some swordsmen units and additional heavy cav.
up to 4 foot contigent...depends on faction, enemy and battlefield. Some swordsmen, spearmen, shooters on foot...whatever i need at the moment.

The only exceptions to this rule are English and Germans.

On early the combo above is generaly the same, but in High and late...

4-6 Heavy cav(feudal/chiv/royal/templars)
2-4 hobbys/mounted sergeants
min 4 longbowmen units.
rest for bilmens, swordsmen (usualy gallows/highlands clansmen or CMAA)

Germans are mainly infantry based and defensive armies are dependant on enemy, that borders with them.

2-4 Spearmen type(preferably the best available) or mix with polearm type(MS or Halb/SHalb)
or...2-4 Swiss armoured pikemen.
2-4 shooters on foot(the best available)
2 heavy cav(knights, the best available)
2 light cav(usualy mounted xbows)
Spare "slots" go to swordmen type units(Swabian swordsmen preferably, in late for additional gothic knights)
0-1 organ gun/serpentine.

For assault, i prefer using my cav mix listed above.

Few units i dislike, so i rarely use them:
Peasants of any sort..
Siege engines...well, i build few for opening castles. Nothing more.
Halberdiers...strange, the chiv are far better, good for garrison duty i think.
Handgunners of any sort. Big noise and little effect. And very often it rains.