I leaned this from a chef friend-Michael who lives and works in Los Angeles at the restaurant Providence. Good fresh fish like salmon needs just to be salt and pepperered for flavor BUT--to grill it so it won't stick on the grill? Lightly brush mayonaise on it to form a film before grilling. It's not about the flavor as much as about keeping the fish together, encased in its own natural flavor, and not left behind on the grill grates. Start flesh side down, then turn it after 5-7 minutes and cook another 4-5 minutes (depending on thickness). It's cooked when slightly resistant to the touch, not firm. I'm a fan of either sushi or cooked salmon but don't favor the in between so popular now; seared and rare in the middle. I like it just barely cooked through. We are in the height of fish grilling season and it's so easy to master and such a bummer when we feel intimidated about cooking it!
Btw--speaking of mayonaise, you can not believe the wickedly good grilled cheese you can achieve by using mayo instead of butter on the outside of the bread before grilling.