It can be as simple or as complex as you want it to be.
I personally have a bigger issue figuring out at what ISO I've shot a roll of film...so on the canister, I put a little bit of masking tape, and mark the ASA as soon as i've bulk loaded a lot of, say, 100 or 400. Then, I keep a marker or pen around me somewhere, and when I'm done with the roll, I mark what ISO I shot at; for example it will be 100/200 or 400/1600
A simple system for keeping track of what's in your camera would be a piece of masking tape, large enough for several notations...for example on the top plate. Simply come up with a symbol for color and a symbol for black and white. For example, an I for b/w and an O for color.
To mark the ASA of 100 B/W film, mark "I"; for 400 mark "4I". Then if you like to push or pull, simply ad + for each stop of push, or - for each stop of pull.
Another option is of course to simply write the numbers, just like in the canisters, e.g. 400/800, but you'll miss out on all the James Bond secrecy that you would get with the symbols.
The advantage of the large piece of masking tape with multiple notations is that you don't have to carry a notebook with you, just a simple pen that you can stick in your pocket. If you write small enough (and the symbols can be really compact) then you can easily fit 10 rolls of info on the tape. WHen you're done, you can simply stick that piece of masking tape on your regular notebook, if you have one, and you'll remember what you shot when, and save some time on pulling out the notebook all the time. The only real reason for all the info on both canister and camera is so that you can remember better what film took what picture.
I should also mention it's very helpful to mark each canister with a number, starting from #1 each day. It'll make sure that you know which film was shot for a sunrise, and which for midday, etc.
Now I should add that if you don't spend as much time mucking with ISO as I do, then just put one color tape on your b/w camera and a different for color. A long piece of tape could be for your faster speeds, and a shorter one for slower speeds.
Hope that confuses you just enough that you know what you're doing.
I never was this organized until I started shooting a lot of video, and all the tapes look the same...simply writing a number gave me both continuity, as well as an idea of what was filmed where...it helps in editing, so I figured it would help with film to, and it has.