One of the most common is Knight/Priest.
Speaking from experience, since you have the option of making several different classes, go ahead and make the Knight/Priest or vice-versa. Then make a Priest/warrior and maybe a Duruid /something. Take some time and try each of them out.
I see many players make a class thinking thats a good one and later down the road, find out it is not "THEM". They then have to start another combination, starting from the beginning. So make 3 different ones and at the low level your at, buy the time each of the classes level, you should have a good idea of where you want to go.
Try to make a class that is "You" as well. One that fits your personality. The closer you are in that one thought the more you will love the game.
Then look for good Guilds or make one and fill it with people you like and do not just invite the world.
