Leonidas and Johhny Mac.....and anyone else.
I have been to a few different training courses offered by Haley Strategic, Alias (Pat MacNamara, Kyle Defoor), and Costa Ludus. I also try to do a bit of local training with an instructor that I respect greatly as well as at Weaponcraft outside of Portland Maine who have a 1st class training staff.
The most important thing that you need for any of these classes is an open mind and willingness to learn. Any of these trainers offer classes in Handgun, Carbine, Etc. Their classes are offered at numerous levels so literally anyone can take them. If you think you have it all down already, then you will get nothing out of the training. Though I have taken them before I still take a Carbine 01 (basic) periodically.
CostaLudus has been fantastic. The atmosphere that Chris Costa establishes is fantastic with the right balance of fun and no screwing around. Safety is priority 1, 1A,etc. Chris' teaching methods are great in that he adapts to different students needs to provide the best experience possible. I highly recommend giving his training a try if you can. I have developed some amazing friendships through Costa that have become some of the people that I trust as brothers.
As I mentioned I have been to a few different Instructors and other than Costa I have only done one session with each. I will be training twice in Wyoming (Restricted/Low Visibilty and Intermediate(Heavy)Carbine) and once in Maine (Vehicle Elements) with CostaLudus this year. I will also be training with Frank Proctor shortly. Last year I only did 2 Costa classes (Carbine Employment2 and Team Building).
To me the most important part is getting at least some form of training in. Too many times people get armed up and loaded down with ammo and don't spend the time truly getting proficient. There are lots of good local trainers but you need to do a little checking and really need to tune your BS sensors. Find a trainer that works for you. Costa, Haley, Defoor, McNamara, Proctor, Weaponcraft, RangeTime......there are many good ones.
Also dont be afraid to travel. I live in RI and will be attending classes in OR, WY, FL, ME this year. It may seem imposing but it is really easy and you will get experiences outside of your comfort zone.
Most classes will require 1. Handgun in service caliber (9mm, .40,or .45) an carbine in 5.56, 7.62x39, 5.45, .300blk etc, proper gear for employing them and for the environment (training doesn't stop because of rain). Specialized classes will require heavy carbine(.308), or bolt gun, or shotgun but you will be selecting those classes specifically.
When budgeting for a class be sure to take ammo into account! That can be a big expense that "sneaks" up on people. For example the Costa Team Building class I did required 4000rds of 5.56 and 1000rds 9mm for a 4 day course of fire. You will truly find out if your gun and your gear are up to the task!
This has been kind of rambling, sorry guys. I hope it is a little helpful. Please feel free to ask away and if there is anything more specific I can answer.
Chris