reserving takes place by posting in this thread, but it is of course no obligation. more a protective measure in case more people want to attend as there will be tickets.
soon tm we will open ticket purchase. we plan to assign a unique 4 digit ID to any attendant, this will be sent via pm and kept secret. the attendant/buyer sends 1 btc and includes his/her ID in satoshis to the transaction. (for example member ID # 1234 will send 1.00001234 btc to the public party-adress) this will keep us from explaining how to sign a message to 1000 people. credit for this idea goes to sebastianju.
you might want to think about escrow?