For judges, I look up what year they were first appointed, and check who was governor that year.
For school boards, city council stuff, etc. it really depends where you are. The town I lived in for the last ten years has a phenomenal local paper, so I got my info on everyone there. The town I live jn now is where I grew up, and my family was involved in politics. I recognize enough names that I can sort it out just from the endorsements.