If someone gets frustrated with you, go to another place. The mom-pop places are MUCH better IMHO than the Cabela's or Dicks where they are just trying to get commission.
Everything else that he said is very good information. I just want to emphasize this piece though. If you're feeling rushed at all, don't be embarrassed to walk out and try a different store. When you're talking to someone about guns, you should feel like you're talking to your friend. They shouldn't really push one gun or another, and they should be more than willing to show you ANY gun you want to see.
I like everything he said about narrowing down what you plan to purchase. There's different calibers, firing mechanisms, and safeties. The firing mechanism and safety features on a Glock are completely different from the firing mechanism and safety on my 1911. MOST of it is personal preference, and there is a safe way to carry just about any pistol you can purchase. The important thing is to get a pistol you're comfortable holding/shooting, and then learn how to shoot it well.
Guns are like cars. There's a lot of manufacturers, and a lot of models within each manufacturer. There's also very similar performing firearms between each manufacturer. The Glock is a great pistol manufacturer, with a great reliability record and a lot of models to choose from. However there's other pistols that are very similar in function, yet differ greatly in ergonomics. Since you're planning on carrying, you can narrow your search down quite a bit. You can figure out what you want to carry, and how you want to carry it.
One of the most important things, that I feel at least, when shopping for a pistol is the ergonomics. Your grip is going to determine greatly in how well you shoot. If it's simply not comfortable for you to hold, put it down and move on to the next one. Trust me, you have enough options. Natural grip is the best way to get a good fit for a pistol. Without looking, point the pistol in a safe direction. THEN look down the sights. If the sights are relatively lined up with how you naturally point the pistol, you're in good shape. When I try this test on Glocks, the front sight is too high due to the grip angle. This is why I'll never own a Glock. You'll understand what I mean when you try this test. Check how much real estate you have on the grip. If the gun feels too big, move on. If you have big hands and it's too small, move on. If the movement of your index finger from the side of the slide to the trigger feels unnatural, move on. You'll eliminate a lot of pistols from your selection simply based on natural feel, and I promise that you'll get a pistol you like to shoot. Once you narrow it down this way, go to the shooting range. This should save you some money from test firing too many pistols that just aren't a good fit for you. Do some research based on brand reliability and customer service as well. By the time you narrow everything down based on feel and brand, you're only going to have a few different pistols to decide from.
