That's such a very broad question! The answer depends on alot of things. Like:
What do you want to use your computer for?
Do you need any particular software programs for school or work?
Are you technically gifted or would you prefer a kinda one-size-fits-all somethingorother that might be a drop-in replacement for Microsoft Windows?
What kind of computer do you want to try Linux on? A brand new super-razoo high-powered megamonster or a humble, aging, modest little desktop?
Linux is alot different from Windows and Mac. It's not more difficult, it's just unfamiliar - for now. Start with some reading, (here is a good place to start) then think about your answers to the questions above and post them here! Then we'll be better able to help you know where to start.
For new users I suggest Mint, or Ubuntu. Mint first, though. It is very user friendly compared to distros like Arch Linux, Fedora, Debian etc. since it is more GUI based. Ubuntu is nice but it is kinda bloated with way too much software.
Debian is VERY stable but does not always have the latest software.
Fedora always has the latest software, but can be unstable.