Definitely take some classes. Sounds like you are planning on that any way.
Always clear the weapon, assume it is loaded. the basics. I am always amazed at how many 'experienced' gun owners have accidental discharges with guns that they swear were 'unloaded.
Putting rounds down range is the best way to become proficient and comfortable with a chosen weapon. In addition to getting a .40, .45 or whatever I would recommend a .22 pistol (if $$$ allow) such as a Ruger Mark 2 for proficiency too. Cheap to shoot and fun to kill a few cans while plinking...