Accessories......
If you are planning on concealed carry, assuming you can get the licence, a good belt is a must. I use a wilderness belt. Someone here has mentioned "thebeltman" for a leather one and I admit I've been looking there too.... So if ya need/want a good leather belt I'd go there. Buy a good holster. Yes, even the 25 dollar fobus qualifies as good. Damn good. I own several for differnt pistols I own. I perfer Galco for inside the waistband carry. Bear in mind you will probably need to loose a few pounds or buy pants one size up for this option. Unless you like and own pants that are on the baggy side. Loose fitting tie-died t-shirts help break up the pattern of a pistol underneath, as do "Hawaaiian" type shirts. In todays society with all the cell phones and junk people throw on their belts concealing a lump is easier than it used to be.
If you have an automatic pistol that has an accessory rail under it you may want a light (or laser/light combo) for it. Slide on the light before you go to bed, now you don't have to fumble for/with a pistol AND a light, they are already there. Go for the light before the laser, has more benefits.
Most autopistols come with 2 mags, get a third. If you went for a revolver get a speedloader (or2) and practice with them. Remember to use dummy rounds for this, you don't want an accidental discharge.
And at this point I "think" you will be pretty much set.
As far as caliber debates I'll keep it simple. Look what police and military forces use. It will insure a pleantiful "stock" of said calibers and chances are they use it cause it works. When the gun owner does his part, as in shot placement and a good powder charge under a reliable hollowpoint bullet design.
Remember as OBG said, you shoot to stop a threat, not kill. Yea, sad political b.s. But its the game you play. Remember, anything short of a CNS shot may not put the threat down immediately. Keep shooting until the threat stops. A man can go 8 to 10 seconds, even after a direct heart hit. It may take time and more rounds, keep shooting until the threat is gone

-Bill Liptak