A great way to get more laughs from your jokes is to add a tag, otherwise known as a topper. A tag is basically a second (or a third, a fourth, or more) punchline without starting a new setup.
I will demonstrate the use of tags, using one of my newer jokes as an example. The first paragraph will be the setup, the second paragraph will be the punchline, and the third paragraph will be the tag. Here we go:
So I'm 43 years old. A lot of people my age are concerned about gray hairs. This morning, I ended up pulling ten gray hairs.
Man, I sure pissed off a lot of nursing home residents!
Especially since they were nose hairs.