There are a million different opinions on carrying a pistol. We'll ignore the good/bad prepared/paranoid arguments; if you're reading this you likely know I fall in the "good, prepared" camp.
Once you've reached that point, it's time to decide what you're going to carry. Wheelgun or bottom-feeder? Caliber? Night sights, day-glo sights, lasers? Inside- or outside-waistband, ankle, shoulder carry?
Made all those decisions? Now it's time to actually FIND the gun you want - and believe me, there's options! Off the cuff, here's a few choices:
Wheelgun: .38/.357/.44, Small-, medium- ,or large-frame. Round or square butt. 1-7/8", 2", 3" barrel. S&W, Ruger, Charter, Taurus.
Auto: .25/.32/.380/9mm/.40/10mm/.45. Barrel lengths from Really Short to Friggin' Huge. More makers than I'd consider trying to list.
Of course, everything is a compromise. Want a .45 with a 3" barrel that weighs 20-odd ounces? No problem - but it's harder to control. .380 in a 12oz gun? Sure thing. Easy to conceal, but not as much stopping power* as the .45. Revolvers tend to be more reliable but have a steeper learning curve and are harder to shoot well.
When I first started carrying, it wasn't a 24/7 thing. I carried my 1911 Government when I thought I should. It was big and bulky and not the easiest thing to conceal, but I shoot it reasonably well and it's hard to argue with .45ACP. I was also still learning to dress around the gun, instead of fitting the gun into my wardrobe. Eventually I bought a Bersa Thunder .380, which is much smaller, much lighter, also very controllable - but a much less powerful cartridge. Very easy to conceal. For the time being, it's nearly a 24/7 piece for me.
But - something about the Bersa just isn't quite "right" for me. Part of it is manual-of-arms: I learned most of my shooting technique on a 1911. The safety clicks DOWN. A Bersa's safety pushes UP. It's a tough change. Maybe I just don't quite trust the .380 round completely. I've been looking at options and finally settled on a S&W 642. It's a double-action only J-magnum frame .38Spl+P. Five shots in the cylinder. Even lighter than my Bersa and overall a smaller gun. Power-wise, it's a hair more than the .380 has, but not by much.
My carry ammo in the Bersa is Hornady Critical Defense - 90gr at 1000fps. Not a bad little round, and I would trust it if I had to. The FTX bullet has tested well, but I have yet to hear of real-world results. The .38, though, opens up the options for carry ammo dramatically. It's an old cartridge, first introduced at the end of the 19th century, and originally loaded as a black-powder cartridge - hence the significantly larger case volume. The ammo I picked up today is Winchester's 125gr JHP +P, 125gr at 945fps - about a 25% increase in muzzle energy over the .380. A non-plus-P round wouldn't see quite as much gain.
For simple size comparison:
The .38+P is on the left, the .380ACP on the right. Tic-tac container simply for scale.
A snub revolver takes more practice to shoot well - which I don't object to. Hell, I like making things go bang! Learning a quick reload requires constant repetition. So how does one acquire that? I'll load up a box of dummy rounds. Sized brass with a crimped-in bullet, but no primer or powder. Sit in front of the TV and practice, every night. Learn the DAO-trigger? Same thing. Unload, unload, unload, then dry fire, constantly. As weather, time, and finances allow, a range trip on a regular basis; weekly if possible. Doesn't need to be lots of ammo; one box of .38 LRN a week comes out to about 2600 rounds a year. For a reloader, that's peanuts - maybe $200 in materials. A couple boxes of carry ammo annually to keep in touch with the +P snap. No big deal.
So which one is the "right choice"? There's lots of good advice out there, and plenty of bad. A new shooter going to the gun store has about even odds of hearing that a J-snub is the "perfect carry gun". A new female shooter will probably be shown a Charter "Pink Lady" or a S&W "Lady Smith"**. THIS IS BAD ADVICE.
The best good advice I can give you: make friends in the gun community. Find a nearby range. Take a handgun class (the NRA and many ranges offer these regularly). TRY GUNS. Find what YOU like to shoot, and what YOU will carry. If it takes pink fuzzy D21s hanging from the grip to do it, that's what you should get. What works well for me as a carry pistol may not work well for you. Try it, shoot it. If possible, try presenting from a holster. Even if it's not the holster you would necessarily choose, feeling what it's like to get a grip, draw, acquire sights, and shoot may change what your feelings are about a particular gun.
Edited to add:
* - "stopping power" is a fallacy. There are numerous formulas and studies and tests done showing that .357Mag has the most stopping power, and nearly as many showing 10mm or .45ACP with the same title. Others will claim that the lowly .22LR is the deadliest round out there. There is no simple formula to determine stopping power. It's a combination of the cartridge, shot placement, penetration, the target's mindset ... a vicious dog might be stopped by a poorly-placed shot from a .22, while there are documented cases of drug-addled criminals absorbing multiple center-mass hits from "guns beginning with '4'." A good hit with a .22 beats the hell out of a miss from anything.
** - Fellow blogger and occasional commenter
JayG pointed out in comments that a 3913LS may be a perfectly acceptable choice for a new shooter's carry gun. He's absolutely right, and it is a Lady Smith. (According to SCSW3, a 25oz 3.5"-barrel 9mm semi-automatic Lady Smith.) I had forgotten that S&W put that label on some of their autos. Personal bias: when someone says "Smith & Wesson", I think "wheelgun". I own four revolvers and they're all S&W. My autos are all different makes. It's what many call "a clue". ;-) So, yes, a small auto may be a great choice. A light snub generally remains a sub-optimal choice for a new shooter (and for many experienced shooters as well).