I clean my bars and the inside of the grips really, REALLY well. Then a small squirt of WD-40 on each one and slide them on. Don't even look at them for a few hours and they should be good to go. I've never had luck with hairspray or anything else to try to make them stick.
If the inside of the grip is clean (as in new), while standing by the handlebar, spray the inside with brake cleaner. Quickly slide it on, allow about a minute to dry. You will have to cut it off. Harley techs do this, and I just added grips to my Pan this way. I never tried it with used grips though.
I've always used a real strong/cheap hairspray (Aquanet) and it always worked. You have to let it dry well though. I know a guy who used that griplock, and it worked well, also. He'll probably need dynamite to get them off though.