You'll need a valid New York State drivers license or a Commerical Drivers License from another state. New Yorkers will need to have a Class D or Class E license. Either way your license must be in good standing. You will also need a Medical Examiners Certificate, you'll need to visit your doctor and make sure you qualify for a commercial license.
Once you are sure you qualify, get the CDL 10 Drivers Manual from your local Motor Vehicle office, or you can download it from their website at dmv.ny.gov. I can not stress this enough, no matter how confindent you are, RTM ( read the manual).
After you've studied enough, you can take the written test. The test is multiple choice with three avaliable choices, but don't let that fool you, it can be a little tough. You'll need to score at least 80% to pass. Make sure you bring a few #2 pencils, and no cell-phones/tablets allowed.
When you pass the written test you can obtain a Learners Permit. You will need your valid drivers license, Social Security card and two documents showing your full name. You'll also need your Medical Certification. It will cost $50; $10 for the written test and $40 for the road test.
You'll need to find someone with a CDL to practice with, they must be present in the vehicle at all time. If you can't find someone to practice with, you should find a professional training service.
This is what all the hard work was for, you're finally ready to take your road test. Get there early with all the documentation you need and ofcourse a commercial vehicle. The test is pretty extensive, and includes topics such as knowledge of air-braking systems, regulations, vehicle inspection and safety operations. If at first you don't succeed, you can retake the road test, it will cost another $40.
Congratulations! Now you've passed your road test you'll receive your results on the spot. You must wait a day to head to Motor Vehicles to get your new license. Make sure to bring all required documentation, always bring your Medical Certificate with you to the DMV. You'll receive a temporary license until your photo ID arrives, usually within 3 to 4 weeks. Now all that's left is driving safely and keeping your license up to date.