Depending on which kind of shower you would like to give, you can either pay for the shower yourself or ask some other close friends of the bride to help out. Also, it is very important that the bride not pay anything. It is important to establish a budget prior to planning the shower that you and your friends can afford.
If you would rather not spend much money, consider having the shower at home and have people bring over food and decorations when they arrive. This will provide plenty of food and you can have a blast decorating before the bride arrives. However, if you decide to have it somewhere where admittance is charged (such as a comedy club) then you need to either have the guests pay their own way or treat them all. If you decide not to treat them, it is very important to let them know the price prior to the shower. The guests will most likely assume you are paying unless you specify otherwise.
It is important to have a working figure of how much you want to spend before you start creating the guest list. This will help you know how many can attend, and how you can make it the best shower possible for the bride.