A "tell" is something that is done unconsciously immediately before a technique. A commonly observed one is a slight blink or squint when attempting to do a technique with power, especially strikes.

How can such a tell be effectively corrected? What kinds of tells are the most common? Are some easier to correct than others?

Oh i suffered with this for sooo long. I used to open my eyes wide and open my mouth as i was about to attack in kumite. No idea why!

I think for me it was a confidence thing. I was concerned about missing or getting hurt more than focusing on what i was doing. Once i became comfortable with distance, timing and plenty of practice it changed a lot.

I definitely think that the "tells" can be conditioned away.

beginners have a lot of obvious tells when they start MA, which gradually get less noticeable as they train longer.

I think its a matter of identifying the tells, and then training in a manner which eliminates them.

For example, drilling front hand punches over and over without a windup from the elbow or shoulder to stop a telegraphing from the body prior to a jab being thrown.

EDIT: I guess what I am saying is: Train train train train. But train correctly.

My old tennis coach used to say, "practice does not make perfect. Perfect practice makes perfect!"

I definitely think that the "tells" can be conditioned away.

beginners have a lot of obvious tells when they start MA, which gradually get less noticeable as they train longer.

I think its a matter of identifying the tells, and then training in a manner which eliminates them.

For example, drilling front hand punches over and over without a windup from the elbow or shoulder to stop a telegraphing from the body prior to a jab being thrown.

EDIT: I guess what I am saying is: Train train train train. But train correctly.

My old tennis coach used to say, "practice does not make perfect. Perfect practice makes perfect!"

This. It's about learning your own tells, either through your training partners pointing them out or by videoing yourself, then making a concerted effort to not do them during training. Eventually you can condition them away. I find my tells are worse when I reach the point of exhaustion. They start creeping in when all I'm concentrating on trying to keep going so in training I've a) upped my cardio to prolong this and b) train to this level semi-regularly and make myself concentrate on a clean performance.

My training partner used to have a great one: before launching any punching combo, they'd double tap their gloves together. When that happened it was simply a case of timing a step off the centre and you'd evade it every time. Think it came from when they were wearing old gloves that used to slip so they'd tap them together to check they were secure.

Tells always seem to get worse when I think about them and when I am near exhaustion. Being aware of them is a good first step, but I still struggle with one in particular which is a slight blink when doing anything with power, especially kick techniques