Make sure it's not twisted when you put it on the bass. Press the string down hard either side of the bridge and nut to get a good witness point. Make sure the bridge saddle height adjustment screws are adjusted evenly (one side can sometimes lift and then it's going to be loose and suck energy from the vibrating string). Make sure that your pickups are adjusted properly and not too close so that the magnetic pull chokes the string. Inspect the bearing surfaces on the bridge and nut to make sure they're even and that the string is not too high in the nut. Can't think of any more right now.