Rub thoroughly with butter mixed with whatever spices you want to use (garlic, ground black pepper, chopped parsley leaves, I also use a little paprika for color) - just enough butter to spread the spices evenly, not too much. Pour some white wine over the chicken before starting to bake/roast it. Take out every 10 minutes, spill the sauce forming in the pan over it using a tablespoon. Turn breast-up only for the last ten minutes. This will give you an all around juicy chicken plus a nice brown crispy skin.
Check the meat every now and then by sticking a toothpick into it. If it goes in easily, the meat is about ready, and you should turn the chicken for the final browning of the breast skin. If no juice comes out after you extract the toothpick, it's overdone already.
Nevertheless, you'll never get the breast to be as juicy as the legs. Chicken breast is simply a drier meat - which is why some people don't like it.
I usually don't put salt on the chicken from the beginning, since salt tends to make the meat less tender if added before cooking.
Depending on size, age and origin (supermarket, young and small chicken need lower temperatures and shorter roasting/baking, farmer's market older and larger chicken need longer roasting/baking at higher temperature) I do my chicken for about 1.5 to 2 hours at 180 to 200 degrees Celsius. You'll need to do some experiments before you get it right.