The thing about teriyaki sauce is that it's so simple to make yet. A lot is a matter of taste, so just adjust the quantities till you get a taste that you like. I learnt this from (of all places) British telly! The basics are these:
Ingredients
3 tbls dark soya sauce
3 tbls light soya sauce
5 tbls dark brown sugar
3 tbls sherry/Japanese mirin wine/Chinese rice wine
6 tbls water
1 salmon steak
Method
1) Mix everything except the water and microwave for 30 seconds and stir until the sugar dissolves.
2) Marinate the steak (works well with beef steak or chicken wings too)
3) Brush with oil and grill or bake at 200 degrees C for 20 minutes. To prevent splatter all over the oven, I wrap my salmon/steak/chicken wings in some foil as a foil packet. The downside of course is that the skin (for wings even salmon skin) will not get crispy.