There's a reason that certain techniques are reserved for advanced ranks in most competitions - these techniques are considered the most dangerous. Either because a) there is a shortened window for tapping before injury occurs or b) the effects of not tapping in time are more devastating than those of most techniques or c) both a and b.
Heel hooks, neck cranks, cervical locks, bicep/calf slicers, and flying scissor take downs all fall in the category of advanced (usually no gi) techniques.
While I learned a few of these techniques as a white belt (the heel hook is part of the fundamental curriculum at my school), it wasn't until recently, as a mid level purple belt, that I began rolling for these during training. Why? Well, safety is really important to me. I've been an athlete all my life and the threat of a possible game-changing injury is quite intimidating. Even more than I want to win, I want to train smartly so I can train for a long, long time.
But, these techniques are legal for me in the no gi division for local and regional tournaments and not training them was doing me no favors. To stay competitive, I had no choice but to begin to train techniques outside my comfort zone. Here's a guide on how I stayed safe and gradually grew more comfortable with advanced submissions:
Communicate with your training partners
I never assume that advanced techniques are on the table. I'm beginning to sound like a broken record, but I always ask my partner before rolling for advanced submissions. I also ask that we not crank on them. Yes, it gets tedious to have this conversation over and over again, but safety is worth this extra step.
Choose your training partners wisely
When I first began playing with advanced techniques, there were exactly 3 regular training partners whom I felt comfortable rolling for these with. These were 3 folks whom I felt very confident would not hurt me and also 3 folks whom I would have no qualms tapping quickly to because they tap me all the time anyway. However, these folks were also better than me, so I caught them with the advanced submissions I was working on approximately never.
They tapped me with these techniques quite a bit though and, eventually, I got better at defending them. I also got better at recognizing danger and knowing when to tap. And THIS made me feel comfortable expanding my repertoire of advanced technique training partners. Eventually I expanded my list to include folks whom I roll competitively with and folks whom I often tap.
Set an example in not being douchey
Are you someone who will go to sleep before tapping, even during a friendly roll? Do you throw some form of hissy fit when someone taps you who you think shouldn't? If so, you may want to rethink your interest in advanced submissions.
One of my training partners likened the heel hook to the knockout cross in striking. Namely, it's a game ending technique that, if you have it, will sometimes get you wins over more skillful practitioners. So if you lose your shit when getting tapped by a lower belt, maybe you shouldn't be playing around with heel hooks. Think about it - is it really worth an ACL tear?
Go slowly
Like I said before, no cranking! Apply submissions slowly and ask your training partners to do the same.
Tap, tap, tap, tap, tap!
This is a non-negotiable. Tap early and tap often. Otherwise enjoy not walking.
It's important to give advanced submissions the respect they deserve and to roll for them thoughtfully and with caution. However, with proper communication and boundaries in place, training heel hooks doesn't have to be much more dangerous than training arm bars.
Hide your feet, friends.
