How can I improve scanning, distance, and escape routes after highway near miss?

[Aaron11]

I recently had a close call on the highway where a car suddenly swerved into my lane, and my instinctive reaction wasn't as controlled as I'd like. I've been driving for years, but I realize I rely mostly on basic awareness, not proactive defensive strategies. I'm considering taking an advanced driving course, but I'd like to start practicing specific techniques now. For drivers who actively practice defensive driving, what are the most effective habits you've developed for scanning traffic, managing following distance in various conditions, and positioning your vehicle to maximize escape routes?