Here is a Checklist - it is not all-inclusive, but covers easily-forgotten and overlooked items.
   
FIRST STEPS
     
Establish a budget.
     
Determine your prime goal
     
Research destinations and resorts.
     
Book air transport early.
     
Consider travel and vacation insurance.
WHAT TO TAKE
 
Diving equipment can be rented. Take your own--
     
Mask - in carry-on bag.
     
Regulator.
     
BCD - although, this may be rented,too.
     
Certification card and Log book.
     
First Aid and spare parts kits.
 
Photographic equipment. Don't forget--
     
Film or video tapes.
     
Replacement batteries, or charger and adapter.
     
More film or video tapes!
 
Personal items (in addition to usual items).
     
Windcheater jacket for after-dive protection.
     
Light, wide-brimmed hat for sun protection.
     
Sunscreen - SPF30 or higher.
     
Towel - don't use resort's room towels.
     
Driver's license - you may want to rent a car.
     
Prescribed medications - may not be available.
WHAT TO LEAVE BEHIND
     
Scuba tank - easily rented.
     
Weights - easily rented.
     
Spear gun - usually prohibited.
SOME QUESTIONS TO ASK
     
Are all dives guided?
     
Are instructors available?
     
What agency affiliations are maintained?
     
What type of dive boats are used?
     
Do they carry first aid kits and oxygen?
     
What is normal visibility like?
     
How long a boat ride to dive sites?
     
How far to nearest decompression chamber?
     
What else is there to do at the resort?