I have used various methods, but found that clear RTV silicone is the best, because it gives you all the time in the world (like 30 minutes or more) to get things positioned exactly where you want them before setting up. And it is easier than most stuff to get the grip off later if you want to without damaging it.
I have used it with Kuryakyn Iso grips many times. Scuff up the throttle sleeve and left bar end. Squeeze some into the grip (more) and around the end of the bar (less). When you slide it on, it spreads it out on the way up, but also builds up excess on the outside which you clean up as you go (so you don't glue your throttle grip to the controls above the grip. It cleans up easily, unlike goop like superglue.
To keep the rubbers in Iso grips (or others) evenly lined up on both sides (with rubbers at about 10 o'clock under your palm on top), always do the throttle (trickier side) first, then it is easy to match the position of the right to the left side second.
With RTV, do not ride for at least overnight to allow good setup. I have had RTV come loose over time, and it is no big deal to pull it off, clean it up, and do it again.
One other point. If you are considering a throttle lock, now is the time for install when doing new grips (goes above the throttle grip). I use the MADCO cam lock, which is spendy, but beautiful billet that looks and functions perfectly on my Valks.
http://www.madcorider.com/http://www.madcorider.com/cam-lock_kawasaki.html 
