Just make sure you back up any important information on your phone before trying anything as the usual process will require wiping your device.
If you have Android 4.4 or lower, I've used Towelroot with great success. It's literally just one click if you use the apk version. It doesn't work on all devices, but for those it does work on, you don't have to wipe your phone or anything.
http://towelroot.org