To develop a good sense of humor, learn some basic jokes from a book or from humor websites, read funny greeting cards, listen to friends tell jokes, go to a comedy club and see stand-up comedians perform, and watch comedic movies. To find your own comedy voice, learn to laugh at yourself, experiment with different types of humor, find something to laugh at each day and look at the lighter side of bad situations.
Very few people excel at all types of humor, so try out different forms of humor to see what works best for you. Some comedians shine when they make spontaneous observations off the cuff but can't tell a simple joke and get a laugh. Some humorists get their best laughs when telling personal stories in front of an audience, while others need to write down their experiences in an essay.
Parroting a stand-up comedy routine, a funny scene from a movie, or a humorous radio show or podcast can teach you about word choice, comic timing, vocal rhythms and inflections. After you are able to repeat a particular performance and get a laugh from your friends, analyze the piece. Ask yourself why the comic took a pause where he did or why he put the words in a certain order. See if you can create a new routine or scene in a similar vein on a topic that is important to you.