I am very short and not very thin, which makes shopping for jeans an absolute nightmare. There are tears nearly every time, it's so stressful. Luckily, I've been really into raw hems these days, so I decided to go ahead and hack off the bottom of my black jeans, which were much, much too long. I had to roll them up much more than I was okay with.
Anyway, the process is really simple. I had cuffed them the last time I wore them, and then washed them that way, which left a crease where I'd need to cut. Another way to do this would be to put them on and cuff them, and then iron the cuff to make the crease (with an actual iron or a hair iron, it's all the same). After you've got the crease, just cut and then pull at the frayed bits to your heart's desire. They don't have to be perfect, that's the magic of the process. I really like how mine have turned out. I wish I'd done it sooner.
Let me know if you try this out!