Firstly, Def learn the laws of your state and states that recirprocate with yours. Laws are written to be interprited, do not try and push the limits into grey areas, if you think you probably shouldnt...DONT.
As for weapons, S&W, they make some nice revolvers, shotguns and rifles, The only semi auto i would consider would be the Smith and Wesson M&P. Stay away from the sigma.
People bash glocks, I think they are ugly, but they are utilitarian. They will work, they are safe and they are reliable. They are designed to be easy to shoot for the person who has never picked up a pistol, and mastered by those who wish to master it. I have a glock sub compact 40. and am going to buy the sub compact single stack 45 very shortly.
Revolvers are also very nice, and easy to carry, make sure its a double action. Look at the smith and wesson J frame, maybe even the officers model with the hidden hammer. My pref is .357. You can shoot full on .357 loads or basic .38s (never shoot 357s out of a 38).
As for caliber, it has to be something you are comfortable with, but i highly suggest a proven Self Defense round, a nice hollow point.
There are a few reasons....Ball ammunition has the ability to hold its weight and mass better, through design. In a self defense situation you may not have the ability to know what is beyond your threat. Due to the fact ball ammo will hold its weight and mass it has the ability to penetrate through the target. This does two things, has less of an effect on the threat and endangers anyone or anything beyond the target, and yes, you can be held liable for anything or anyone hurt....especially if you end up fatally wounding someone innocent.
Now we have ammunution covered, ill tell you that i strongly suggest 45 and 40. A 40 caliber will give you the carry capacity of a 9mm and not be far off from the ballistics of a 45. but being as we are comparing a 40 to a 45, why not just get a 45.
What stops the threat is actualy hemmoraging and blunt trauma, you want to do as much damage as quickly as possible. ENTER .45. The 45 is a very slow, very heavy round. This means that with a good hollow point, theres a very good chance all of the bullets energy will be absorbed by the threat, and not pass through. A 9mm is a light high velocity round. Yes Police Departments use them, however, they dont do the damge a 40 and 45 will. Its not a comfortable feeling knowing your going toe to toe with a bad guy, who you already shot and hes not stopping....thinking "damnit, i need a 45". Its a horrible feeling.
Enjoy your CCW. Be responsible and dont make the good guys look bad. Get ouf of situations if you can and use it only...ONLY as a LAST RESORT where you belive death is imminent if not used in a defensive situation.