1) Placement: With piercings, you want to make sure the jewelry flows with your anatomy, giving the impression that it belongs there. Complementary rather than random. Keep in mind that everyone's anatomy is different, so some things work for one person better than others.
2) Color: Body-piercing jewelry has evolved dramatically over that last 10 years. The standards are titanium and surgical steel. They are both a high-polished “silver” color. These can be great if you want that throwback 90s look. If you want the ironic grunge look but want something a little fancier material-wise, white gold and platinum are available. All four of these materials look bolder on the skin and give a bit more of a dramatic effect. If you have a pinkish skin tone, rose gold will be the most subtle choice. If your complexion is darker, yellow gold will look the softest.
3) Size: If you are getting a stud, make sure the size is not overwhelming to the area it will be living in. If you choose a ring, keep it closely fitted so it isn't an eyesore. Think about it like a pair of jeans that fit vs. a pair that's 1 or 2 sizes too big for you. The only disclaimer with this advice is, when making a new piercing, we have to overshoot the length and diameter to compensate for swelling and healing. With studs, the length is usually hidden, but hoops can show the extra room.