There are times when as a photographer, particularly if you are taking a lot of photos at one time, when you want to take a note. Perhaps you can read the photo number (although most DSLRs actual have countdown counters, which give you and approximate idea of space left for new photos). A simple approach is to have a simple code for just photographing hand signs or things in you hand like the lens cap. Here is my photographic version of such punctuation.
Full Stop, a marker that perhaps end one series or starts another, or just a reminder to take a good look at the previous photo(s). This can be used for a variety of breaks or just simple visual markers when looking through a large collection.
Panoramic Sequence, and direction of shooting. I must admit i don’t use this all the time, because a panoramic series is usually pretty self explanatory. When I have used this I will add this marker photo before the panoramic sequence is shot.
HDR Bracketed Sequence, in this case I am taking 5 a photo sequence. Alternatively you can just use 3 fingers for a simple set. This is another punctuation marker that I normally use to precede a sequence.
Battery Change, this is just my way of recording when I changes my battery, looking back through your photos and finding the previous battery change photo, then just subtracting the new photo number from the previous gives you the battery life in terms of number of shot per battery charge.
Whilst I normally take both Jpeg & RAW, I usually delete the RAW version (which can be large) of any punctuation photos.