Keep a blog where you "document" any issues you keep running into. By the time you're done with the post you'll either remember it or if you don't you'll know exactly where to find the answer if you need it.

I would actually recommend Wiki (specifically wikimedia) software for this doing this.

It can act very much like a blog, but also brings along features of many Knowledgebases, like versioning of information. Sometimes problems evolve, and being able to keep track of that is beneficial.

And how will I find stuff in my own pile of notes? Googling :)

Happens to me all the time.

I use Evernote to keep track of the most common bash commands, API calls, syntax specifics, etc. Flash card format, e.g.

Title: Check if object is in a NSMutableArray Content: containsObject: