If you're having that much trouble missing, you can actually tape the syringe down to your arm to reduce movement of the syringe. Might help. It's not really good to keep re-registering, it increases the chances of damaging your veins. Possibly better to reduce the volume of the water you're using, depending on the solubility of the drug.
To reduce bruising, press down on the area right after pulling out(sterile gauze or cotton is best), and shoot in less fleshy areas. Wait a little bit to pull the syringe out after the shot too, a few seconds will do, to reduce chances of leakage(well, it's called infiltration actually, heh.) IV tech 101 really.