If you're going to do it around the neck, best thing to do is the crook on the inside of the elbow, not directly across the wind pipe. If you look at the link in my previous post it talks about that some.

Mr Wiseman did much research on law enforcement vs martial arts, and why there was a high amount of injuries due to law enforcement over martial arts. What he found was the person who was being choked knew how to relax in martial arts, where in the case of law enforcement, the person doing the choking is exerting so much force, and the 'perp' was fighting back there was a higher amount of injuries.

Also, please be aware that age as well as diabetes has a large influence on the bottoms' safety. Danger goes up in proportion with age.

For those just learning, the method I found that helps the Top read the bottoms panic signal best was using the hand over the mouth method, and the bottom putting a free hand on the forearm of the Top, pulling the Top's hand away from the face when panic comes (it will come, and is natural regardless of the level of trust). Once you are able to learn the non-verbal signals using this method, stepping it up to hand on neck, and arm around neck you will be able to have more self confidence in the relative safety of what you're doing.