I use a free piece of software that I can run on my phone, tablet, and pc called Evernote.
What I love about this software other than it being free is the ability to keep separate spirals. I ahve some for work, personal, and then I have a beer recipes spiral. For each beer I take notes on my phone of mash temps, water additions, anything that went wrong, or if I used new gear.
Probably the BEST part is I take a picture of the final product and do tasting notes and you can attach the picture right from your phone into the note. That way when you go back months or years later you can see what it looked like to see if you needed to tweak it any.
You can take voice notes with it too inside of each note. It’s probably the most used app I have. It doesn’t require any installs on a PC, you can access it anywhere by going to evernote.com
edit: one other thing I keep in there is a copy of the Wyeast/White labs chart for when I am in the brew store and they are out of something. I just pull up the list and pick a new one or a substitute.