Like most, my biggest hurdle has been chord changes. I have found the most progress when attempting to apply them to an actual song. Not that the song is better practice but I will stay with it longer as it begins to sound like it should.
And one of the few things that my middle-school band teacher actually taught me was: Practice, practice, practice. But I never learned to apply this lesson until I decided to try guitar as a hobby.
Edit,
Tortex is the name. I thought it had robbed off of all of them but one was still ok