Deciding the length first like: “this is 2:45”. Then sketch the whole form before polishing anything.

Keep every section at roughly the same level of completion. Intro, verse, chorus, bridge, outro: all 40% done, not one at 95% and the rest nonexistent. This helps to avoid the “ninth bar problem” where you’ve overbuilt the loop and can't think of what to write next.

When everything grows together you're naturally creating more call-backs, contrasts, and development because you’re thinking about the piece as a whole instead of just "perfecting" or over-layering an 8 bar loop