Comedy Answer: Just take off your clothes. Easy fix.
Originally Posted by Sang
More Serious Answer Just Because: Something that a LOT LOT LOT of people up to and including purple belts don't pay enough attention to is defensive grip work. It's second nature to guys with Judo backgrounds, but lots of times BJJers will happily give up a 'non threatening' gi grip to their opponent in order to work their own game. That's something you can get away with once you have a really broad knowledge base about what is and is not a threatening grip. More than once I've dismissed one of my instructors gi grips as him trolling me only to suddenly find myself being choked stupid by it 20 or 30 seconds later.
As a defensive measure you simply have to take a step back from your attacks and defend those grips immediately. Someone grabs your clothes? Grab your clothes in the same place and take it back. Grabbin your collar? Posture. Grabbing your sleeve? Strip that grip.
If they can't grab you, they can't choke you.
If they do get a choke going on you then grab the pieces of clothing they are choking you with and pull down and away while you work to escape.