A lot of the newer tamers do not understand their profession. Taming is the most varied skill out there. This website is proof of that. While many people go out of their way to be antisocial and ruin the game as much as possible, I have a feeling that since you are reading this faq, you want to avoid being an asshole without knowing it. So how can one avoid antisocial behavior?
This effects more than just tamers! If a creature you just tamed is blue, most players will hesitate at killing it. Why the hell would anyone want to kill your abandoned critters? Many animals are an excellent source of hides for tailors. Young warriors will need some of those creatures to raise their skills. Contrary to common belief, monsters will not attack blue creatures all the time. Why this happens is unknown, but monsters will only attack blue tames if a human player is present.
Renaming your tames is helpful to other tamers in the area if you do not kill your tames. For a second tamer to tame a particular creature, they get an increased taming difficulty. A renamed creature will serve as a beacon for tamers who want the increased difficulty or as a warning flag to those who barely have the skill to tame them at their original levels. If you are working in an area where no other tamers are, I strongly recommend just killing off your tames to cut down the chances of taming the same creature twice.
You cannot gain any skill for taming a creature you have tamed before or had transferred to you. This is for your own benefit. If you kill your tames, you will be less likely to tame the same creature twice. A creature can only be tamed by so many people before no one else can tame it. If you find such a creature, it should be destroyed. You might want to read the guide on how to kill tames.
Would you name your real life dog "a"? Then why name your virtual pets "a"? There is nothing more degrading to a pet than to name it after a letter in the alphabet. Commanding pets is easy if you set a say macro for each of your pet's names. When taming creatures for skill, give them a short name (other than "a"!) like joe, pete, al, etc. You can just as easily make a release macro for your favorite short name, or spam a confused pet with commands to force it to go wild quickly. This also helps distinguish which creatures you have tamed, as opposed to someone else's tames.
I think that purposely releasing dangerous creatures near innocents is a cowardly act. If you want the player to die, at least take a count for it. Also note that releasing aggressive pets near players in a Trammel ruleset will endanger your account.
If you see someone taming a creature, be courteous. Let them tame the creature. There have been times where I have spent a half hour on a wyrm, only to have someone recall in and fight me for taming rights. There's nothing wrong with taking turns. Though its not a requirement, help the tamer out. Taming is a small world, and some day, they might return the favor (be it good or bad, depending on how you treated them).
If you have a pet you can barely control, you should not be out hunting with it, since you can't control it well enough to keep it from killing other player's kills. Hunt responsibly and keep your pets under tight control.