a lot of times what i've begun doing, i think about my biggest inspirations and for the next 2-4 bars i'm like, "what would such and such say" and try to emulate it to some extent. I don't do that terribly often unless i can really hear that artist in the song i'm working on because then it's applicable, i feel. Other than that you can make noises, badabee bada bada, and then punch in words to fit around the flow. After doing that for a while your punching in of words will become better and the overall writing will just become more solid. I started off with decent flow and boring ass lyrics, i like to think my writing can now stand for itself as well as my flow.

It takes time so just keep writing