I focus on:
1. can I get out quickly and cheaply if I'm wrong.
2. where I might get out of it goes my way or partially my way.
3. when to get in.
Usually, I form a rough idea of each as I see the setup potential. Then as the setup forms I'll fine-tune. Of course, I'm a swing or intra-day trend trader, not a scalper, so I have a minute of two, often more, to go through the loop.