This is as simple as it gets. To increase your sense of humor watch more comedies. You learn more effectively when you immerse yourself in a subject
If you really want to develop your humor, then try to take something ordinary and make a joke out of it. There is a hidden joke behind every little event and situation you come across.
In the beginning, you don’t have to be creative. Just go out and do some research! The internet is full of great resources for jokes, humor, puns, funny pictures, stand-up, etc.
We have all got some friends that we find funny. Go ahead and spend some time with them and learn what they are doing to be funny and how they do it.
All comics will face criticism on a regular basis. The thing about jokes and your sense of humor you have to understand is that everyone won’t always get it.
Knowing your audience is a key point to making them laugh. You can go overboard with your humor and end up offending or upsetting an audience that doesn’t want to hear it.
Silly humor can be a solid starting point for some audiences, but it can get old quickly. It also might make you look immature (which can be bad at work and in the eyes of some people).
My last little bit of advice is practice. Comedy is something where it all comes down to Delivery and Timing. If your delivery and timing are not correct even the most hilarious jokes can fall flat.