Why should you get training?
Drills are great for practice and can significantly improve your skill level, "IF" you know how to do them properly. While the physical components of the drill are needed, the most important part of how to do a drill properly is understanding the purpose behind the drill, then you can practice the drill with that specific intent.
Some drills or practice exist to focus on a specific skill or sub-component of a skill. Taking your time to do a scored bench-rest or prone position precision rifle shooting target practice can help improve breathing, sight focus, trigger control, and other accuracy based skills. A different drill and mindset would be needed if you wanted to improve draw to first shot (such as draw from a holster dry-practice or dry-fire drills).
Before you go to training, you should decide what you expect to get out of that training. Are you new to shooting sports and looking to get basic skills? Are you experienced and want to learn self defense based techniques? Then look for a class that matches that need. Many quality companies exist and some have cycles of travel into areas that may be close to your location.
Keep in mind that selecting a class also means that you should be evaluating the company and/or instructor who will be teaching/conducting that class. Don't pick someone who has a widespread bad reputation or is known for sloppy instruction. Be aware that anyone prominent will have "some" bad things said about them, so look for the general trend, don't focus on the one or two bad reports. Many trainers/teachers/instructors have different ways to teach as well, keep this in mind during selection. If you find there are methods/attitudes/styles of instruction you don't wish to be involved in, avoid those instructors/groups/companies.
If possible try to get some kind of training at least once a year and there are a lot of different courses from a lot of different people so in a few years you can get a diverse selection of training and experience. (Examples: Improving speed or precision, defensive mindset, trauma first aid, rifle skills, pistol skills, shotgun skills, etc.)
Some thoughts on finding training or trainers who might be worth considering.
First: look for an inexpensive course or instructor in your local area. Some instruction is better than no instruction, and often these people are better than you might expect. This can be a benefit, especially if you don't have a big budget, because you wont need to travel or pay big name prices (even the often ignored NRA classes can be a good place to start).
Next: there are a lot of big names out there (Massad Ayoob Group, Front Sight, Thunder Ranch, Tactical Response, Sig Sauer Academy, and MANY more). If you want to do a big name course, they can be great, just do your research and match the training you want to the classes and instruction offered.
Last: be aware that you will only get out of the training what you put into it, and I'm not talking just the $$$. If you have a bad attitude in any way: "I don't want to be here", "I already know enough", "why am I doing this", etc. the training won't go that well for you.
Popular or well known Trainers/Schools