Should You Group or Solo

World of Warcraft has bonus experience if you group. Blizzard are a bit vague about the amount of bonus for grouping but it's there.

So it makes sense to group up for extra experience, right?

No, not necessarily.

If you are looking for a social game, the chance to interact with other players, the sure go group. Run some instances. If you want to level fast it's about the worse thing you can do. Forming a group takes time. You will spend so much time looking for a group, or looking for somebody to join your group, you will lose far more experience than if you were out hunting and gaining some xp. I've spent 2 or 3 hours looking for a group on the less popular mid-level instances - usually falling apart for lack of a healer or tank.

If you happen to see somebody on the same quest as you throw them an invite if they are already there at the quest site. If you see a group of four ready and waiting at the instance summoning stone, get in there quick. Otherwise, don't bother. If you find somebody in the zone chat channel for the quest, the chances are that they will take so long to get to the quest it would have been quicker to do it solo.

I've leveled a lot of characters to 65, and three to 70, and I've had much faster leveling solo.

Now obviously this advice is somewhat class-specific. It make sense for full-time healers to go for the grouping option and they normally don't have trouble getting a group quickly. Hunters are the other extreme. They can solo "hard" mobs all day long. Most classes fit somewhere in between the two.