Have you ever played an MMO before? If not that's probably for the best because when I first started it up I found some of the UI stuff, particularly cosmetically, to be pretty annoying compared to games like WoW or tOR. So if you have played any of those games try to go in with an open mind to the aesthetics of the game. I wasn't sure what to expect and found myself let down by some things, so it was like a small barrier to get over right at the get go.

Aside from that just be prepared for usual MMO stuff. maybe 10-20% of the time that you solo queue you're going to get grouped up with a real asshole and they will absolutely ruin a dungeon for you. Try to set goals for yourself that are separate to hitting the level cap. Maybe you're going to really focus on saving for a mount, or you want to try a bit of every class. Just something that can alleviate the dullness of grinding.

Mostly I'm just tempering your expectations. If you're able to level the whole way up with some friends you'll most likely have a lot of fun and it'll make it go pretty dang quickly.