Watching the whole film first
I watch a film from start to finish before writing a word. A trailer can hint at a lot, but it cannot tell the whole story, so I judge a release on what it actually does with its scenes, performances, and pacing.
Trailer breakdowns follow the same rule: I read what a promo signals about tone and structure, then hold my conclusions until the film proves or contradicts them. Spoilers stay out of the opening lines, and any plot detail is flagged clearly.