Scenario:
You are going on a 2 week holiday to Bonaire in the Caribbean and plan to do several dives. Naturally you want to find the best possible IDC (international dive center) with the best service and quality for your needs.
 
A first step might be to search Google for "Bonaire Dive Center". Some of the results are:

• Buddy Dive Center
• Blue Divers Bonaire
• Bonaire Eat Coast Diving

As you can see these websites vary pretty much in visual style and quality, but there are some similarities when it comes to content. Most of them cover the concepts:

• Staff
• Contact
• Prices
• Photo/gallery
• Teaching (courses)

But that do you really need?
Being a diver myself I've looked at several IDC websites and based on my personal requirements and concluded that I need the following infomation on a IDC website:

• Courses (what do they teach, PADI vs CMAS vs ...)
• Trips & Sites (where can I dive and what can I see)
• Prices (what does it cost - trips + equipment)
• Photo & Video (real view on the sites - down use low quality images!)
• About (about the dive center qualifications)
• Contact (prebook trips etc)

Further there might be branding, news and order areas for various information.
What else are you looking for at your IDC websites?
If I've missed something (which I might have), please drop a comment and describe what kind for information you are always looking for at an IDC before booking your dive.