Hi Scarletina,
I also made my own planner and here are my tabs (not in any particular order):
1. dress (bride/bridesmaids) / accessories
2. decorations / color combos
3. food / cake
4. photography / videography
5. venue info - ceremony/reception
6. calendar / checklist
7. destination information (mailings/print-outs/contacts)
8. a pocket to keep track of receipts
For a simple countdown calendar, I just tore one out from one of the bridal magazines to keep me up on what things should be done and checked off every month.
I feel that a DIY planner should be whatever you want to put into it. If anything catches your eye in a magazine, tear it out and put it in there - it's really your idea book. =) It's something to show your wedding coordinator, your family, or your bridesmaids, or your vendors to give them a sense of what you want your wedding to be like!
Good luck and have fun with it!