I try to compose my songs completely in my mind before I record anything. For me that takes longer to produce a final product but it's usually worth the wait. If I draw blanks for an original song I do a cover tune. Listen to Miles Davis' version of Autumn Leaves then my version. I had it completely worked out in my mind before I picked up an instrument. The end end result is what you hear and it's right on what I had before I started recording. For me, it keeps my imagination "ready" for composing.
P.S. I forgot to mention that it matters not if your song sucks or not. I just saying it's what I do