For your Ann Summers party, or for anyone who wants to do a raffle, this can be done a couple of ways.
The straight forward way is to sell tickets and have three or four prizes depending on how much you have taken in raffle money. Sell the raffle tickets as people arrive. Draw tickets and give prizes to winners.
Or you could do a snatch raffle. Here you draw all the tickets, giving a rize for eac ticket. However, once all the prizes have been given out, the person with the next number to be drawn "snatches" a prize of their choice from someone else. This carries on until all tickets have been called. The guests with the prizes at the end keep them.
Another twist for your raffles is to seal the prizes in a bag so winners don't know what they've won until the end.
Further advice: Take two bags of raffle prizes with you - a good raffle and a normal one. Judge by the sale of tickets which bag of prizes to use. Even if sales aren't brilliant, you should make loads on the raffle.
Click this animated image!