All the World's a Stage
This article is here to teach you how to roleplay a criminal successfully. While they may be able to just simply steal things and commit crimes. What's the fun in that? This will help you make your criminal the best possible.
What is written below is not set in stone, nor a rule you must follow, it is simply a guide on how one can choose to RP - and there are many choices out there!
A little bit of information about criminals
Criminals are lawless people only restricted by what they want to do. They can be considered Neutral Evil. One advantage criminals have is that, like said before, are only restricted by who they are. Some may just be the thief, but not try to hurt others. While some just kill whenever possible. There are many ways to roleplay a thief, but with those many options can come a big restriction in what he does. For example, a killer would not just walk into Stormwind waving at the commander of the guards. If he even walked into Stormwind he would be thrown in the Stockades. If you are planning on spending a good amount of time in Stormwind, you better have a good reason.
Thieves have some advantages that come with them to consider.
As said before twice, you have no limits besides what roleplaying and your character will allow.
It's also possibly easier to get money in the game with the robbery and everything.
With advantages come disadvantages, and this is no exception. You will want to consider these before making your character a thief.
You are hated by the guards. You're a criminal, guards hate criminals.
Things to ask yourself
There are some things you'll have to ask yourself when roleplaying a thief. Does he work alone or does he prefer to stay with a group whenever possible? What's his motive behind thievery? How far of lengths is he going to go to steal something? Is he a true criminal or just confused? If he is confused, does he try to help the Alliance/Horde whenever possible? Is he stealing for personal gain, a group he's with, or his faction (Alliance and Horde)? When you've asked yourself these questions, then you have most of him figured out.
But, before you ask yourself these questions, you have to make sure that they fit together perfectly. A person who prefers to fight alone is probably not going to be very trusting of his allies and may keep an eye on them. He's also probably going to not be trusting of his commanders and may do things his own way. You have to make sure everything is going to go together. But don't think that the starting emotions of your character are going to stay that way throughout his journey through Azeroth. You'll want to develop him and show change in times of great tragedy. A reckless person may try to be more careful when a close friend is hurt or injured from his/her's actions. But the changes are not going to be instant. They are still going to be reckless for a little bit, more than likely unintentionally, but soon they will learn from their mistakes.
Even criminals have limits
Now you may be thinking to yourself, "Criminals have limits!? They're murderous villains with no real emotions and will do whatever they want!!" Truthfully, that's what criminals are generally portrayed as a lot in the media. But some criminals are quite the opposite. The limits will determine who he truly is and the options of how far he will go is determined by those questions you ask yourself. I doubt a criminal who would not kill a person is going to join the new Defias or some other organization of people who kill. He's more than likely going to just rob nothing more than a few gold and run off, and may even show hesitation in that!
The major thing is what determines how he does things he does. If he's a person seeking vengeance, he's going to be willing to do whatever he can to stop the person he's after, and since you are playing a criminal, you are probably stealing his prized possessions to hurt his pride and money to fund your missions and make it harder for him to do stuff. And may even cause distrust among his ranks if he has any. Or sending some of your best (or worst depending on your character's personality) soldiers to destroy his base.
Some things to remember
Criminals can not just steal things for absolutely no reason. You need to add depth to your character and make him come alive! A great way to start in your criminal's motivations and history is by looking up the various criminal organizations throughout World of Warcraft on WoWPedia! Maybe your character was one of the Stonemasons but wanted to get their revenge in your own way? Or he is one of the few survivors of the Defias looking to help get the organization back into action? It's all up to you! So, now the rest is up to you on how to roleplay your character.