Well, chances are that if you are not good at it without the piercing you won't be any better after it is pierced. Nothing beats good old fashion know how. I will say that it does make it a little more interesting and kissing is a lot more fun.
No. The risk involved with the piercing is that if it is off to the side and nick one of the large blood vessels, then it will not clot. This can be dangerous if not taken care of. The basic risks involved with Tongue piercing is the risk of eroding teeth, gums and the bones on the top of your mouth. This comes down to basic placement and jewelry size and is why it is so important to reduce the length of the barbell ASAP. For more information on Tongue piercing go to the Tongue Piercing Page and Aftercare Instructions for Oral Piercings.
The Angle that the piercing is done at.
A Lip Piercing is pierced almost vertically with the natural curvature of the lip. This means that the jewelry is less likely to come in contact with teeth, bone or gums. Thus meaning there less chance for damage. Also you have more jewelry options then a Labret piercing. You can wear a ring, curved barbell, etc...
Labret piercings are pierced almost horizontally or perpendicular to the tissue. In other words straight through below the lip. This cause increase chances of contact with gums, teeth and bone. Due to the angle and the fact that the jewelry would have to wrap around the lip, rings are not an option. Also a barbell may in fact cause more damage. So you are limited to either a Fishtail Labret or a Labret Stud. Placement is also a factor. A lip piercing is just below the lip, while a labret is much lower depending on the jewelry type in the shape of the mouth.
Yes, having a metal object aka jewelry in your mouth that has contact with teeth, gums and/or the bone structure of your mouth can cause damage. It is why it's important that the piercing is placed correctly and that you wear jewelry that fits correctly. You can reduce damage buy wearing dental acrylic jewelry and softer materials like gold that will give before your teeth will. However, especially with jewelry that is always in contact with parts of the mouth issue may happen regardless of placement or jewelry. It is one of the reason that DaVo will not do smiley piercings.