In the end, you only can really know what's funny to you. For me, I love the romantic comedies. I love my son Rob's movies because they have thoughts and ideas in them and they made you laugh at the same time. The best tip is just to keep writing and sending it to people. Once you get a good piece, send it out.
Comedians have to be aware of who to send it to.
If you write jokes, send it to a comedian. Send a screenplay to a studio or an agent. But if you believe in it and other people like it, just keep writing.