I started learning the standard shorthand, but when i got into it, I realized that the amount of effort needed to make it fast enough was not really practical for my purposes (taking notes in class). So, instead, I took the basic strategies I learned and created my own shorthand, designed for my classnotes.
The way I did this (which may or may not be the most productive way for you) was to go through my past notes and highlight/underline the letter combinations that appeared the most. For example, some of my most used ones were “th”, “-ion”, “-ly”, “-ss”, and “-i-e” (ex: -iTe, -iVe, -iRe). At that point, I went through them and created a symbol that would mimic the shape of the letters (or at least it would in my head).
It took a while to get used to the system, but after a few months of practicing with book notes and class notes, I got to the point where i didn’t even think about it anymore. It really helped me to keep up with what was being said (and also, it was readable enought that I didn’t have to go back and transcribe it again). The biggest problem comes when someone asks to borrow your notes :-D