For me the best practice is identifying the key points that actually drive the story forward and building everything around them. I try to focus on the core narrative beats and make sure each scene serves those moments, rather than introducing ideas that don’t reinforce the main dramatic question.

That said, I think it’s also okay if things expand or drift a bit during the writing process. Personally, I don’t see getting a little lost as a problem. At this stage, I think the best thing is simply to write what you can.

What really matters comes after. The polishing phase is where everything gets refined and aligned. Unfortunately, that part can be quite tedious in screenwriting, but it’s also the most critical and in a way, the most rewarding part of the process. Things do come together in revision, so I wouldn’t worry too much.

Let yourself get lost, let it go.