Although they all work in somewhat different ways, they have some things in common.
You can get minions to do things with "ask" or "order". All minions can be ordered to assist, unassist, follow, attack, focus on a particular creature, or leave. Totems and spectres can also be ordered to defend or protect.
If you order one to attack something, the target will attack you as well.
Minions cannot be successfully ordered to attack priests or followers of the same deity as the summoner (and will disappear if you attack those).
If there are multiple minions in the room, especially if some of them are being controlled by other people, it may be necessary to be more precise when you refer to them. You can refer to a specific priest's minion by prefacing the name for the minion with the priest's name (this works for your own name, too).
l warrax whirlwind
You can also refer to "minions", "summons", or "creatures"--as in, "order minions to leave"--to get all the minions you're controlling.
Controlling multiple minions at a time is more difficult. First of all, attempting to summon a minion when you're already controlling one or more can result in not only failing, but having your existing minions disappear. Some types--notably creeping dooms and spectres--will attack you before leaving (with spectres being much more persistant about it).
Even if your skills are up to the task, though, it will cost more gp to summon a minion if you're already controlling some. In general the extra cost seems to be half the base cost of the ritual, times the number of existing minions. So if you try to perform Dust Devil--a ritual that normally costs 50 gp--while already controlling a totem and a dust devil, it will cost 100 gp instead (50 + 25 + 25).
All minions will disappear when their time is up (the exact amount of time they'll stay on their own varies). However, you can cause them to stick around longer if you "feed" them gp.
More gp at once seems to make them stay longer (although it may be more difficult), and small amounts of gp (such as 50) seem to make them depart even sooner than they normally would.
There is a faith.rituals.special skillcheck involved--failing this can cause the minion to leave immediately, like so:
| You concentrate on the misty woman, but feel your energy dissipate into the aether.
The misty woman dissipates into the air.
Every minion has a warning message it gives--that it is preparing to depart--several seconds before it leaves for good. You can still feed them gp at this point (although it appears not to work if you've already fed them gp).
They will also disappear when they die, when you order or ask them to leave, or when you log out.