How can I come up with ideas for jokes?

I like to take very basic premises and then just find one element to emphasize, dramatize, or elevate. So, for example, people often freak out when you don't answer your phone or respond to text messages, right? So one skit I came up with was all about this person whose phone died, and their friends started overreacting by assuming that they'd died. The humor there comes from that one little amplification! You don't need to come up with something ground-breaking every single time. Often, it's just about those little touches or changes.