For just starting out I would recommend going to Gander Mountain or a similar store and purchasing a prepackaged brine. They work well and you can vary to suit your own taste the next time. I smoke a lot of Salmon and I use an electric heat source. It is much easier to control and the biggest variable is the thickness of the fillets. Oil your racks before placing the fish on them. I prefer skin off so I can remove the "Brown" flesh just under the skin and along "mud vein" down the center of the fillet.

210 should be a MAX temp but shoot for 185 - 210 it works best for me.

Alder is a great for fish but I have used everything from Cherry to JDanials chips and mesquite