I've worked on a lot of these things, with varying levels of success.

• More consistently remember something they want to watch out for in various situations (especially social/fast-paced situations)
• One thing I did for a while was pick 2-3 things I was working on per week when socializing, and review them before I went into social situations, then reviewed them afterwards.
• Build new mental patterns/habits (in general).
• I recently built an app for this. The idea is to combine spaced repetition, visualization, and Murphyjitsu to gradually condition new mental habits. It's here if you're interested.
• Effectively observe social situations as they occur, in person, to learn from the interactions in order to develop social skills (bonus if the strategy allows for one to not appear/be awkward or violate social etiquette)
• I spent lots and lots of time around strangers, and saw what good/bad responses I got. Its' not perfect now but vastly improved.
• Somewhat less relevantly, banish aversions to human connection/intimacies that make things like eye contact difficult/overwhelming (the aversion is mostly habitual at this point)
• I did a lot of exposure therapy. For eye contact, this as easy as going on youtube, searching Eye contact practice, and finding one of the many videos made to practice this. For other things like touch, you can start with imaginal exposure (just imagining the thing and relaxing), and then gradually work to escalating exposure in the real world.

More generally, the PUA community has done a lot of work on how to improve social skills and social IQ. There's a lot of BS and toxic frames in that community, but also a bunch of great exercises and data, if you're willing to sift through.