These are just my suggestions...
1. Read books covering submarine warfare, particularly that of WW2. You will learn a lot, and a great many of your questions will be answered within their pages. I recommend "Steel Boat Iron Hearts" and "Torpedo Junction" and perhaps even for the spirit of adventure and a retrospective "shadow divers".
2. Watch movies covering submarine warfare. "Crimson Tide", "Enemy below", "The Hunt for Red October", "Das Boot", and "U-571" (i dont respect the film U-571 from a serious sub fan and history buff standpoint, but from an entertainment standpoint...which is what it was meant to be... it is an okay film) these movies will help you learn what submarines are all about.
3. Learn the keyboard commands inside and out.... and form an understanding of when to use each command and WHY you are using it for a given situation. this is learned only from practice.
4. ask questions on subsim every time you encounter anything that you have a curiosity about. THE ONLY STUPID QUESTION IS THE ONE YOU
DONT ASK!
5. DO NOT download ANY mods for Silent Hunter III until you have developed a good understanding of how the game works, until you have developed your own play style and tactics. ***only when you have come to appreciate the game in its default condition can you begin to realize the talent and achievement of the modders out there and truly respect their products and play them the way they were meant to be played.
anyone else care to take it from number 6?