Here are some set-ups that you can use to help you practice writing punch lines. Don't worry about set-ups being boring. Sometimes the simpler they are, the more effective the punch line can be. But they can also be weird statements that catch the audience's attention.
“I feel weird being naked in front of my dog.”
“I'm not a good cook.”
“I hate getting my hair cut.”
“They say that one out of every 300 cars is stolen.”
“Did you know that dolphins sleep with one eye open?”
“Women are smarter than men”
“I'm bad with money.”
“I read a study that said women thought bald men were sexier than men with hair.”
“Paris Hilton has a new show coming soon.”
“I like pencils better than pens.”
“Television commercials confuse me.”
“I hate taking the subway.”
“I hate getting my picture taken.”
Those are just a few to get you started. When you're writing your punch lines, try using the different techniques you've learned to see where they might fit best. Always keep in mind what the audience is thinking when they hear the set-up. What are their expectations, and how can you play with those expectations to make it funny?
Feel free to alter the set-up to get you thinking. Instead of: “I hate taking the subway” try “I love taking the subway!” or “I always get nervous taking the subway.” You might actually hate taking the subway, but your hatred might come through better if you start out saying you love it. The audience will assume your statement is true and your hatred will become the twist.