Q: or an A section), how do you go about making a transition into a new section (voice leading? music theory tool? Wild guessing? Wikipedia?)? THANK YOU!
A: do a fresh run-through from the beginning, at the exact tempo. the more refreshed you are, the better this will work. It works the best if you haven't heard the song in a day. do a fresh run-through, and then just as you start to approach the end of what you have, that is when lightning will strike, if it does. listen very closely in that moment, and try to gather as many details as you can about what you think you are hearing next. Another trick which often produces results is to imagine the song is taking place in a scene. imagine a visual story for the song to take place in. Also another thing i almost forgot to mention, in case you are not doing already, try to use words/language for this