The best kind of fundraiser will vary depending on what your group is all about, but in general it's important to think about a few different things:
1) Cost to put on the fundraiser - try to rely on sponsors/donors as much as possible to minimize your out-of-pocket expense. This is easier if your group is an activist group and can get sponsorship from local agencies that support your cause. Or if you're in a recreation group, you could try soliciting places like sporting-goods stores for donations of prizes or loaning equipment. I put on a great Battle of the Bands in high school and got tons of donations for food, prizes, a professional photographer, etc by simply writing letters and advertising my sponsor's names on everything and sending thank-you letters. You'd be surprised at who will donate if you only ask. Also, you can't advertise too much. Get a street-team.
2) Maximizing profits by balancing ticket price with accessibility. Figure out what's reasonable to charge people if your event is charging for admissions. While you might be tempted to go for the higher end of reasonable, it's probably a better bet to go a little lower and hopefully attract a bigger crowd. Don't forget to set out a donation jar. You probably wont get much that way, but it cant hurt.
3) Make your fundraiser available to more than just a small target group. While the Back Country Club might offer ski-waxings as a fundraiser, doing something like that automatically limits your profits. Putting on some kind of humorous production is a good way to attract guests. The promise of a good time (like a humorous "burlesque show" put on by the obviously unprofessional members of your group accompanied by stand-up comedy and other talent or talentless routines) will surely generate more revenue than something like a movie showing + bake sale. [Now I wish I had a reason to fundraise - putting on a burlesque show would be so much fun!! I might have to patent that idea!]