Maitnence

Well I want to get into the more mechanical part of owning my car..I have tried staying away cause I have a habit of taking things apart..putting them back together then wanted to make them better and then have them not work.....but umm anyway I figured since my req. maitaince light just popped on This is a good of time as any...I was jsut wondering what that I should change/clean/inspect before I switch the light off. Mm thx in advance.