A friend of mine recently complained that lately leveling has been extremely tedious. Even with characters he might feel excited about at first, he eventually gets bored after just a few quests. We talked about this for a little while, and he brought up the fact that if he was going to play WoW by himself he might as well play a single-player game instead.
It got me thinking that, in spite of all the demand people have for more solo and casual content, this is significantly better when we play it together. Even when I play by myself, my eye is always on my friends list to see if someone I know is going to show up and chat with me. Thinking about my friend's problem, I thought maybe it would really help if he and I were to go questing together -- so we found the two characters we had with the smallest level gap between them and we decided to go at it. Rather than just just going through the motions of killing the various enemies listed on our little quest sheets as if we were buying groceries or something, we made it into a neat little roleplay experience.
In fact, there are lots of quests in the game that are very appropriate for roleplaying. When you get together with your friends to level up and quest together, you can focus on the quest that has the deepest possible connection to your own character, or the one with the most intrinsic storyline. Of course there are many other throwaway quests you can do along the way, like "kill 10 Generic Humanoids" or whatever, but it works best to pick one that seems to have some meaning to you or your character and start there.