"Don't push in the clutch all the way"

Pushing it all the way in engages the clutch brake which stops the gears from spinning inside the transmission. You need that for stopping and starting. Not so much when shifting.

 

Double clutching like that usually ends after school when you start floating. But yes do not depress all the way unless stopped. Pressing the clutch all the way applies the clutch brake which is bad while moving and trying to shift. Just a quick jab to take it out of gear and another quick jab to pull it into the next gear. Watch your speed and rpms and don't rev it hard. It's a diesel not a race car. One suggestion I have is to set your seat right. Set it so with your leg extended you can't put the clutch all the way down unless you point your foot down too.

 

Normally you would only have to push it until it's side by side with the break pedal. 1/4 way or so

 

You can ask your trainer if he will teach you to float your gears (meaning shift without using the clutch at all). Will he teach you to do that?

 

Adjust the seat so you have to really reach to put the clutch to the floor...that way you can do a full leg extension and the clutch does not go to the floor. If you need to use the brake clutch, just slide ahead on the seat a little so you can push it to the floor. Usually at a light or a stop sign you are shifting into your start up gear before you come to complete stop, so you should not need the brake clutch then.

 

You'll get the feel for how a semi truck shifts vs how a manual in a car shifts, personally I only use the clutch when starting from a stop and then I float the gears for each shift and downshift, but schools and some companies want you to double clutch when shifting, just tell yourself this with each shift, am I going to make more work for myself by pressing the clutch all the way to the floor or am I going to sit back and relax with only pressing the clutch about a quarter down with each shift, you'll get the hang of it, practice practice and most importantly, stay calm and concentrate on what your doing. Good luck to you!!

 

Also in training it's important to master the double clutch becouse in some states you are required to double clutch to pass the skills test

 

The clutch was only put there so you would have a foot rest!

 

OP --
Read the bottom paragraph first, then read the rest of the article:
http://www.answers.com/Q/What_is_a_clutch_brake_on_manual_heavy_duty_truck_transmissions