How do i write lyrics?

Okay i want to be in music really bad. My two favorite artists are kid cudi and lupe fiasco. I want to be on lines of those two kind of. How do i get to a level of their expertise? How do i practice? Do i just write a bunch of random punch lines?, write a lot of stuff that rhymes on paper? Write whatever pops up in my mind from freestyling? What do i do?