Question on D&D ranged attacks

I was curious what the rule is on characters like rangers and wizards using ranged attacks to attack enemy's while there is a teammate in line of site? Is it possible that you are arching your shot over your teammate or do you have to move out of line of sight? Also for enemy's far away trying to shoot a teammate who is trying to shoot me, but there is a teammate in their line of sight, do they have to shoot my teammate?