The most important factor for me is that the salmon has to be high quality - e.g. wild and fresh. Previously frozen and defrosted salmon will not have the same texture as fresh salmon. It will likely turn out dryer. It's hard to make frozen salmon as awesome as fresh salmon. For me, making fish is a treat. Wild fresh fish is more expensive than previously frozen fish, but I treat it as a seasonal special occasion treat.
The second most important factor when cooking salmon is to not assume that one cooking time is going to work each time you make the dish. It may sound annoying, but it really is done when it's done. Each salmon fillet is of varying thickness and density, and therefor will cook at differing rates. Over time, it gets easier and easier to tell when the fish is done just by looking at it and smelling it... but here's the trick for checking doneness: stick the tip of a knife blade into the thickest part of the fish. Put the blade against your lips, if it's hot/warm, it's cooked through. If the blade is cold it needs more time. This allows you to pierce the fish with minimal destruction, no need to slice it in half and ruin the fillet.
Everything else is incredibly simple. You can add whatever favorite herbs or sauces you like to your salmon using this method.
Roast Salmon with Rosemary and Lemon
Salmon fillet, either whole or cut into individual fillets (I like one's that are 6-8 oz per person)
Lemon, thinly sliced
Sprigs of fresh rosemary
Salt and pepper, to taste
Olive oil, to drizzle
Preheat the oven to 425°F.
On a parchment or foil-lined baking sheet, place the salmon skin side down.
Salt and pepper the fish. Top each fish with thin slices of lemon and sprigs of fresh rosemary (either left whole or chopped fine). Drizzle the top of the fish with olive oil.
Bake for 7 minutes, then turn the pan around (or rotate pans if making salmon on two sheet pans). Depending on the thickness of the salmon, check on its doneness after another 5-6 minutes. Most salmon cooks in about 14-15 minutes. Serve immediately with your favorite sides. Leftover salmon keeps for 2 days in the fridge.