I use lotus organiser, just because I have for a long time
We have a general agreement, how many we want to do in a week/month, and I book, and its up to the others to tell me well in advance what they cant do in advance, I rarely cancel.
The idea of a shared resource is great, never try to work with more than 1 diary, thats when you get duplications.
I have a standard form i send out with a copy to be sent back
Date
Time start
Time Finish
Max playing time
Fee
Payment [on night, cash, cheque,]
Special instructions
Saves loads of arguments