Great topic.
Before officially moving to UK long term, I decided to spend my summer (2.5 months) visiting the UK and exploring as much parts of the country as I could. This sort of cushioned my move of the "great migration" and I felt a little more confident and comfortable because I knew that I was only going to be in the UK for a couple of months. Now I'm ready to make the big move when my visa arrives.
For those of you who don't get to do this, I'd recommend the following:
-Research the place that you'll be living in. Look at forums like this, Google & Wikipedia the town, and ask yourself, is this the place you really want to move to?
-Join meet-ups that have the same interests/hobbies. I don't know where you'll end up, but if you're in a city, you can try meetup.com
-Keep lines of communication open with your loved ones back home. I've opened up an instagram specifically for documenting life in UK. I need every bit of support from folks back home while living abroad.
-Be excited for the magical journey ahead of you! The UK is a beautiful and magic place, far different than my home in California. California - definitely beautiful to some eyes, I've lived here all my life. I'm ready for adventure and UK is calling!
Hope this helps!