I write a lot of code comments. It helps me structure my code and make it a bit easier to scan, but it helps my future self too: understand why I did something; alerts for pitfalls or not so obvious code structures; etc. I've also written apologies to other developers who may come across my code one day. :P
Something that I've started doing in the past year is "tagging" my code: adding hashtags to act as bookmarks to help me find key lines of code that are related to something I'm working on or something I did in the past.
// #tags #kludge #revisit
// #tags #2015rebuild #govLimits
They always start with "#tags" so I can find all the tags later (doing a search inside project files) and remind myself of what keywords I used, and then follow up with something more descriptive about whatever I'm tagging.