A little overdone is better than underdone...you do NOT want salmonella! Been there, done that, not going back!
If you're baking chicken in an oven, keep it covered except at the very end and add a little water or broth at the bottom of the pan. If it's on a bbq grill, use a medium heat so it doesn't boil the juices out (marinades help if you have time, even just smothering it with some spices or mustard and let it sit for an hour or over night). If it's in a pan on the stove, med/high heat and you can always add a little chicken broth to keep it moist if you're cooking it covered, or a little olive oil on high heat if you want to brown it uncovered.