Initial Learner's Permit Process
Go to your local DMV, and they will give you a free workbook
There will be 12 chapters, from which you need to go through four chapters coming to your pre-exam test
Go back to DMV to pay the fee of $15 and give the test with 150 questions (50 questions in each section)
You only need to get 70% or higher in each section to pass the test
In case you fail any section, then you need to repeat the above process.
When you pass the test, it will give you a learner’s permit. With this permit, you will be able to drive a CDL vehicle or air brake kind of vehicle but accompanying a CDL licensed driver in the vehicle.
Final CDL License Process
The learner’s permit will last for six months. Go back to DMV and pay a $20 fee to get a CDL license.
An instructor will be with you while you are driving the car. If you drive properly and follow all the rules, you will receive your CDL license.
One of the best ways is to first get your dot physically, then pass your commercial learner's permit exam, then pass your DMV road test. It includes a pre-trip inspection, in-cab inspection, air brake inspection, and a variety of different back-up maneuvers.
The requirements are a little different in each state so you need to know what the procedure is for your specific state.
A call or visit to your local DMV could help you out with that.
You also may need to consider a CDL school, not all states require that though.