It is an art to turn any negative situation to your advantage, and no less so when roleplaying in WoW. In the fine tradition of "turning stumbling blocks into stepping stones," it pays for a roleplayer to reconsider a number of in-game situations which seem to get in the way of roleplaying, yet which actually offer a special opportunity to showcase your creativity.
The biggest stumbling block WoW roleplayers trip over is often some aspect of the game mechanics themselves. Your roleplaying may lead your character into a deadly conflict with another player, for instance, and yet even if you kill the other in a free-for-all PvP arena, he or she can just resurrect and be back to normal in a few minutes. Alternately, you may find an epic BoE drop off a Skettis Kaliri and be hard pressed to explain how a rainbow-colored owl was flying around with a huge sword inside its body. You may even ponder why every single ogre you've ever seen is male.
Naturally, of course, there are ways around all these problems -- it's just a matter of finding plausible reasons for things. You may say to your bitter rival, in the event of a deadly conflict: "I do not kill fellow members of the Horde! We shall duel for honor and be done with this!" Likewise, when recounting your discovery of your BoE epic sword, you might explain: "As I killed the strange owl, I suddenly noticed something gleaming in the grass just next to its corpse! This [Blinkstrike] was lying there, sticking out of a stone in the ground!" Your character might even make an effort to explain away in-game oddities: "I have deduced that the entire race of ogres must be hermaphrodites -- both male and female at the same time! They are so ashamed of this that they all hide the fact, pretending that ogre females are hidden away somewhere!"