What is Taming?
/tame CREATURE : A Ranger-Only skill, taming attempts to bring the target (a monster/NPC) under your control. Your success depends on your level compared to the level of creature, your Charisma and the creatures "tameability." Note, not all NPC's are tamable.
Taming Tips
One of the most vexing things about taming is the limit. You are restricted to 5 NPCs (this includes summoned monsters from spells like Druid's plantcall, and Sorceror's unkelming and warpdoor) per party. Once you have 5 monsters tamed, if you keep trying to tame other NPCs it will just keep on failing without telling you why. There's no message telling you you've reached the limit. Always be aware of how many NPCs are in your party, even if they aren't in the same room as you, they still count.
Taming is essentially "infinite." Meaning you can tame while exhausted, which is a bug but can't really be stopped and isn't punishable. Many monsters, even for a Stalker, take dozens of tries to tame, so don't give up! Set your macros and sit on them till you've got the monster you're after, but again, remember your limit! It's frustrating to realise you been trying to tame something for 5 minutes when you already have 5 monsters in your party!
While you can appoint someone else as party leader, disband and tame more creatures, deliberately getting around the restriction is considered exploiting a bug and is a punishable violation of the terms of service. The level of punishment often depends on the judgment of the staff member you're dealing with, but it is an offense that can get you banned.
If anyone attacks a monster in their party it will no longer be tamed. It will only attack the character attacking it, so long as they both remain in the same room. If the monster is drug off the room or the player leaves it becomes completely "wild" again.
Monsters with healing spells, like Zombies for example, will heal members of the party (usually just the party leader) from time to time as if they were healing themselves, as long as they are at full health.
Tamed Thieves, Bandits and such will steal from players and monsters, but give the gold to the party leader. This applies whether you are on the same square with the monster or not, so you can be walking through town gaining gold from your tamed monster until someone kills it or you disband the party.
Some monsters cannot be tamed, or can only be tamed once in a very very great while, so rare that it might as well not be possible. These are usually referred to as "untamable." Most boss monsters (those that drop OADs) are untamable along with a few regular monsters, like Gnolls. Most things you'll come across can be tamed eventually.
The monsters in your party can be healed with spells to keep them alive, but it can be tricky to heal them all. When a healing spell is cast at a monster, it goes straight to the first monster of that type in the room, until it is fully healed. (Note, monsters gain the FULL benefit of healing spells cast on them, no matter how many hit points they need to reach full life, meaning you can "over-heal" a monster to more than its original hit points.) To heal all the monsters in your party, select each one by right clicking on it, choosing "Cast" then the healing spell. If this doesn't work, command all the monsters to halt following, right click on the injured monster, command it only to follow, move off the square and heal it, then back. It can be tedious, but it's worth it to keep your beasties alive.
Turning on attacks for tamed monsters, until the monster you are leveling on is grave, then turning auto attacks off will result in faster times between kill shot bonuses, usually resulting a faster experience gain. Be careful not to let your monsters get the kill shot when doing this.
Unless in a strong party or over-quested, Player Killers rarely try to attack a Ranger when he or she is leveling with a few strong monsters in tow. When choosing monsters you should choose wisely and collect a variety of monsters, depending on what you want, pure meat shields should be chosen on AC, dodge ability and, most important, hit points. Monsters that can poison or paralyze (Like Yetis and Winter Wolves) are especially useful when combating other players.
The same shield of tamed monsters that works so well for discouraging PKers is also great for exploring. Taming is a Ranger's strongest point, and a good Ranger or Stalker rarely goes anywhere without a few beasties in tow.