Every state has different standards when it comes to issuing driver's licenses, and that holds true for commercial driver's licenses (CDL) as well. Even before looking into particular schools, one should find out the requirements in their own state, and then seek out schools whose training programs meet at least the minimum standards.
The Professional Truck Driver Institute (PTDI) is an accrediting body which certifies truck driving schools that meet certain criteria. Although not every good truck driving school chooses to seek certification from PTDI, this is a great starting point to find reputable schools. Some state's education departments also keep lists of approved truck driving schools, so this could be another helpful resource.
Things to look for in a truck driving school include one-on-one instruction, time spent driving, theory instruction, quality equipment, knowledgeable instructors, and job placement assistance. While the truck driving market holds lots of opportunities, having placement assistance is both convenient and reassuring. Also, if a driver is interested in seeking endorsements, such as hazardous materials or passenger, he should look for a school that offers training in such an area.