Salmon is very versatile and leds itself to all sorts of methods. But since this is your first time here are a few very simple suggestions.
Rinse the fish off, and pat it dry. Oil lightly EVOO. Season with salt, pepper, and some smoked paprika if you have it. Grill to medium rare -- no more than medium. Although more forgiving than many fish, poorly cooked salmon is not pleasant. You want it cooked to the point where it's firm when you touch it, but not so done that it flakes easily. Treat salmon almost as you would steak by allowing it to a rest for a minute or two before serving.
There are some tricks involved to prevent salmon from sticking to a grill -- especially an outdoor grill. If you don't know, ask.
Or, prepare the fish as before, but without oil, and poach it. Poaching in or above a light fumet or court buillon is also good. You want a bare simmer -- don't allow the liquid to boil. Be careful not to overcook the fish. Poached fish is very nice served well rested and at room temperature.
With regard to saucing and garnish, in this case and as a general rule it's a good idea not to do anything too complicated or uncertain when trying a protein for the first time.
If your skills and diet permit, sauce with hollandaise. Otherwise, anything with plenty of lemon is a great choice for your first effort. A lemony homemade ailoi / mayonnaise would be very nice, especially if you're going to serve the salmon room temp or on the patio.
Fresh, poached asparagus is a perfect garnish for salmon -- especially hollandaise.
So is nearly any salad. Grilled salmon (no sauce) is one of the few things which can share a plate with classic Caesar salad and not get wiped out.
PS. Rereading this post I realized I hit the lemon pretty hard and it needs some clarification. Lemon in just one thing on the plate. Quoth the maven, "never more."