Every situation and dock is different.
Personally...so as not to allow the ski to go under the dock...I'll tie off on the leeward side of the dock with a single line attached to the front. That'll allow the ski to drift harmlessly away from everything that could hurt it. If that isn't possible think about what affects the movement of the ski...ie wave action...wind....wake from traffic...ect...and what the corresponding movement will have the ski coming into contact with. Don't forget to inspect the edges of docks and floaters...you're gonna want to be looking for nails that've come loose from boards and are sticking out past the bump rails....if there are any bumpers/pads/folded fire hose...ect.
I haven't found any "bumpers"(that attach to the side of a pwc) that I'd trust after the first contact....with anything.
Aside...if you don't have the room to allow your ski to drift on a single line away from the dock...tie off fore and aft to the leeward or down wind....down wave side....when ever possible. This one small thing will help you keep the dings(to your hull) to a minimum.
