Many of us have grown accustomed to storing our wallets in our back pockets. When you become a truck driver you will need to stop this practice. The wallet will create pressure on your butt and cause you to sit unevenly creating an unnatural twist in your back bone. This will, over time, cause you some real pain in your butt and lower back. You should get in the habit of carrying your wallet in your front pocket. This also prevents your pocket from being picked.
Another tip for the new guys coming in has to do with the air ride seats. Some drivers will inflate the seat all the way up and enjoy the fact they are sitting so high but they will have leg cramps over time. This is caused by the seat cushion putting pressure on the backs of the drivers legs thus restricting the blood flow. The proper adjustment for an air ride seat will keep your feet flat on the floor while sitting straight in the seat. Lower the seat until there is no pressure on the backs of your legs. The only drawback to this is you may "bottom out" when going over rough roads. If this happens then you may want to inflate the seat a little more and SLOW DOWN on rough roads and railroad crossings.