Soak the planks overnight if you get your act together. Even an hour should be fine. Get the grill heated to about 400 degreed. Put the planks out there for about 3 minutes and flip them over for 3 more. They will be producing some smoke which will be a welcome memory should you have transitioned recently from charcoal/wood to gas. Put the salmon right on the planks and cook about 10 minutes. One of the best fish I’ve ever tasted from the grill!