Drive with people you trust. In team-driving, it's imperative that you're comfortable with the person you're traveling with. If not, sleeping becomes increasingly difficult. Your partner should be courteous when making turns, hitting speed bumps and backing up, as well as when using a CB or radio. If your partner isn't a courteous driver and makes a lot of noise when you're trying to sleep, getting your rest will be an uphill battle.
Add extra padding to your bed. The constant vibrations of a truck in motion can cause discomfort and, even, injuries. Your shoulders and neck are particularly sensitive. Adding a foam pad provides comfort and reduces the chance of impact trauma.
Use earplugs. The road noise, coupled with music from the radio and conversations over a CB, can make sleeping seem impossible. Eliminate the distractions by using earplugs that filter out a lot of that noise. White-noise headphones are another option that can achieve the same effect.
Use a sleep mask. The headlights of oncoming cars at night or sunlight during the day can make resting uncomfortable. Using a sleep mask can take some getting used to, but it will block out the light and help your body relax, allowing you to fall into a more relaxed state of sleep.