I always used my phone for taking notes. I would just create a new note with date and stream name.
Since I always reviewed USGS flows, I would record that data, the weather, the time I entered the stream, air temperature, water temperature and the overall clarity of the water.
Upon exiting, I would record all of that data again with exception to USGS Flows and then the amount I caught.
I did not record each and every fish as they came, I would just mental note them and then record total fish by species and anything over 16". Markers on your rod make for quick measuring. I would also record any odd events, good or bad, whether I thought someone had fished it before me, being chased by a landowner or any nice deer I had seen for possible future hunting.
I then e-mailed the data to myself and kept it in a spreadsheet. You could however set up a spreadsheet on your phone and skip that step.
The idea behind the data for me was to "figure out" the optimal conditions of how a stream produced. If I caught 20 on one day with certain flows, temps., clarity, etc. and then 80 on another day, I could then start recognizing that stream's most optimal conditions as well as use that knowledge as a starting barometer for new streams. Ultimately, I learned how to pick the best stream to fish on the day I went fishing....and then sometimes the stream picked the day as well.
For anyone learning who has caught the bug of pursuing trout, I HIGHLY recommend taking notes, it will make you a much better trout chaser.
I do not take notes on trout fishing anymore. I won't claim to know everything but I've learned a ton and can make any day as good as it can be.....there are times I am still wrong though.
You will never get away from that! but you can minimize it.
I have however returned back to note taking on other species as I've caught the saltwater bug with my kayak as well as pursuing other freshwater species. Musky and Walleye are a mystery to me still (as to many) but sooner or later, I'll figure out the puzzle as my notes will help me make better choices.