More a longer-than-comment add on to other replies:
When useful I write a note by hand and photograph it.
This may be photo context or email address / contact details of a subject or whatever.
Usually this relates to an adjacent shot. If not I add the frame number. As I tell people - if I can find the photos a year from now I can find your contact details. If I can't find the photos then it doesn't matter.
I sometimes expose a fully black or fully white frame as a visual marker when viewing as thumbnails, that lets me rapidly locate chosen images - whether notes or the image proper.
In cameras with still + video capability you can leave a spoken 'note'.
When using multiple cameras (often) at the beginning or end of a session or day,with each camera I photograph my watch at a minute boundary immediately after the minute has 'rolled over' (eg 11:23:00). The EXIF then contains the camera time and the image shows the watch time. This allows me to then synchronise the image streams so that they time interleave correctly.
If absolute time if important I photograph my internet synchronised time on screen at a computer minute boundary. This gives camera time to absolute time relationship and allows all camera images to be properly time synchronised.
Getting OTW :-) - If photographing sequences- maybe panoramas or related shots or ... , I may photograph an outstretched hand at the start and my foot at the end. Maybe I should make a collection of these :-).
If adding contact details after a sequence of photos I may add one extra shot of the person concerned so it is time-adjacent to the details. If there are several people in a group photo and I wish to be able to relate names to the photo I may write down the name and a brief description of each - often based on clothing colour or style.
Sometimes other means are required: