Why lead taming? The days of trapping a creature behind an obstruction have completely been done away with. You have no choice but to be in harm's way. Of course, there is always para taming, but magical creatures tend to cast spells on themselves until they are free, which also breaks the taming attempt. Para taming also causes a freshly tamed creature to take 14% skill loss, instead of the usual 10%.
Never go out unprepared. Always take plenty of healing necessities (bandages, regs, pots, etc.), just incase you get too close or get a bit of lag. If you're going to be attempting magical creatures, take a few trapped pouches. They seem to take delight in paralyzing you as you try to walk away. Try and get more taming skill than just the minimum requirement. Your odds of success aren't so great at the bare minimum, but improve significantly for each .1 taming you have. It is recommended that you attempt to tame them with no less than .5 above the minimum requirement. And never underestimate the need for friends. What are the odds of both of you lagging at the same time? It's even better if your friend is a good peace bard.
Make certain you are very familiar with the personality and quirks of the creature you are about to tame. If you are ever in doubt, the tameable listing has a profile on every tameable creature, including their quirks, skills, and abilities.
It is also extremely important that you do not have reactive armor or spell reflection active while attempting to tame aggressive creatures. If they get too close or throw a spell at you, it could trigger those defensive spells and disrupt your taming attempt. If you must have a defensive spell active, use protection, since it will lower your chances of being disrupted while spell casting.
If you click on the thumbnail, it will display a basic map of how close you will need to be to your angry little friend. The inner ring of white cloth is how close you will need to get to it in order to initiate the taming attempt (which is no greater than 3 tiles away). Once a taming attempt has successfully been initiated, you simply have to remain between the outer ring of white cloth (which is no greater than 7 or 8 tiles away). Generally, at the default UO screen settings, the creature will need to remain entirely on screen if you are directly above, below, or on either side of it. If you follow compass north, south, east, or west while lead taming, it becomes a little more difficult to judge when you are getting too far away.
If you are a tamer lucky enough to have peacemaking, you'll have a fairly easy time taming aggressives. Simply target peacemake your hopeful new pet. This kinda puts them to "sleep" for a little while. The skill delay should not be too long, and you can get a few taming attempts in before it "wakes up" and starts chasing you again. While under the effects of a target peacemake, the creature may snap at you and then fall back "asleep" again. Just stay a few tiles away while taming and you should be fine. Even while they're "asleep", if they have the fire breather target switching behavior, players near by that refresh the screen will trigger it. You will usually be able to get in at least two taming attempts before peacemaking (at GM) wears off.
Creatures that are angerable can still be peace tamed. Every time they are angered while under the effects of a target peace, they will still walk in your general direction. Once a successful taming attempt is initiated, the angerable creature will fall into "sleep" mode.
For those of you without peacemaking, it is a little more difficult, but entirely possible. Most high end pets, such as dragons or wyrms, may need to have their health dropped to make them a little easier to tame. By dropping their health, it will cause them to move significantly slower. This is recommended for all high end fire breathers (dragons, mares, fire steeds, etc.) so that their breath attack does significantly less damage.
When you attempt to tame the creature, you should always be moving. For every step forward the creature takes, you should take one in the direction the pet is moving. About 95% of the time, they will be chasing you, but fire breathers will switch targets to any player that runs by. If you start to lag, KEEP MOVING. Usually, you'll end up just fine if it's just a few packets dropped here or there. If lagging persists for long periods of time, you should stop and try another time.
Now wasn't that fun? Under most circumstances, the creature should stop attacking you once it is tame. However, if it breathed fire or casted a spell at you a split second before you tamed it, it will continue to fight. You will need to give it a stop command or make yourself invisible somehow to get it to stop. For politeness sake, you want to try and remove your new pet from the subserver you are currently on so that new creatures can spawn for other players to enjoy. You also don't want it stomping off after whatever monster near by targets it, especially if it was weakened to make it slower. This is part of the reason why I recommended taking more than just the bare minimum skill: it will give you better control over your new pet.
Hopefully you enjoy your new pet and that it is a swift bonding for you. Don't forget to feed it right away to start the 7 day timer.