Questions from a beginner to some more experienced riders

First I just wanna do some background and say I’ve had my license for about a year but only bought my bike a month ago (Iron 883 in case you’re wondering). I’ve taken the MSF beginner and advanced course. I’m also very excited to be part of the community!! My questions are; what is your best advice for new riders to help improve skill? What’s the best way to work up to riding on the highway (so far I’ve been sticking to the streets)? What is your best advice for new riders to not be a squid? And most importantly what does dragging your rear brake mean/how do I do it? I’ve been told dragging your rear brake is a good habit and skill to learn because it makes slow maneuvers much easier but the descriptions I’ve seen so far I’m still not understanding. Hopefully someone can help, I’d really appreciate it!Edit: formatting and grammar via /r/motorcycles https://www.reddit.com/r/motorcycles/comments/di358p/questions_from_a_beginner_to_some_more/?utm_source=ifttt