How do I add comments to photos?

Hello,
I would like to know if there is a way to add comments to my photos as I edit them.

For example: if I'm reviewing a set of photos I usually make my initial cuts (reject/rate) my photos and then go through a second pass (sometimes a couple days later) to make my adjustments if needed. I would like to leave myself a note with certain photos that says something simple like "crop this, adjust colour, fix blemish etc." so that I don't forget what I had in mind.

My only idea was to use keywords, but then I have to delete them all after. Is there a better way to do this?

Thanks in advance for any advice!