There are some things you should know before getting a lip ring, though. Most lip piercings, except the vertical labret, are both external and oral, meaning that you'll have to care for it with two sets of treatment. So, it's a little extra responsibility when it comes to keeping it clean and encouraging it to heal.
Also, since a portion of the jewelry is inside your mouth (whether it be the back side of a ring or the flat disc of a labret stud), that always poses a risk of damage to your teeth and/or gums. It means you need to be extra diligent about your dental care and check every day for signs of wear or deterioration. If you see any, you should probably remove the piercing. I know that's not a pleasant prospect, but severe tooth damage and gum erosion is painful, costly, and sometimes irreversible.
Another thing I like to stress, particularly with lip and oral piercings, is don't smoke! Your body heals much better when you don't smoke anyway, but lip and oral piercings get particularly irritated by cigarette smoke and all the nasty toxins that are in it, not to mention it hurts like hell.
You should also know that a piercing fistula for a CBR or circular barbell will be somewhat curved, while a labret stud piercing is straight. Because of that, it's not a good idea to try to switch jewelry styles, because they won't rest properly in the healed fistula, which could irritate it.
I recommend nothing smaller than a 16 gauge piercing for the lip; 14 gauge for those with full lips.