The first thing to do is get the study manual from the DMV. I have heard there was legislation coming that would require attending a school, don't know if that went through yet, but the manual will say if it is required. The problem with some schools is, they want to process as many bodies as they can as quickly as possible. This results of these types of schools are a lot of common sense challenged people driving very large trucks.
I have heard Salt Lake Community College is inexpensive and they have a very good rep for not graduating dumbasses.
UTA used to be a quick easy way to get your CDL. They would help you get it in turn for a 6 month work contract. Don't know if that is true or not still.
I prefer guys who find a small company that is willing to train them and pay for their CDL. I think starting with a good, worthwhile employee and training them for CDL results in a far better driver.
You need to take the driving test in a vehicle that is classed in the same type of license you want to get. I.E. you can't drive your motorhome or 5th wheel.
Lastly, the legal climate in trucking is so rough right now, that if you intend to get a CDL you better be the most patient, understanding, law-abiding driver there ever was. Tons of drivers get sued and do jail time for accidents where another party was the cause. You are watched and recorded in everything you do. This is the reason I will not exceed the speed limit ever. It's about litigation. Not safety. Utah county I-15... 54 miles per hour all the way through the construction zone. Everytime, cuz I like my truck and my house.