At least as far as purchasing a BCD is concerned ... ask the LDS if you can try it out in a pool first. If they refuse, thank them for their time and go find another LDS.
Most LDS will try to steer you toward one particular style of BCD or another (as will many in here). The fact is that all have trade-offs ... and what's important to you may not be what's important to the person who's trying to sell you the gear.
Some things to consider ...
Fit and comfort are important. That's why you want to try the BCD in the water before purchasing. See how it feels with a tank and regulator. Make sure the shoulder straps don't ride up around your ears when you're sitting inflated at the surface. Make sure the tank feels secure on your back ... roll around in the water and see how it feels. A tank that wobbles around back there will make your buoyancy control much more difficult, and your diving less fun. Make sure that when you inflate the BCD it doesn't feel so tight that it restricts your breathing (only really a problem with jacket-style BCDs). Make sure the inflator/deflator buttons feel right for you ... some models just aren't that intuitive (to my concern), or may not feel right in your hand. Make sure you can get the air in and out of your BCD comfortably ... or try another model.
Where you'll be diving determines how much weight and exposure gear you'll need. That, in turn, will determine how much lift you need in a BCD. Don't buy something with way too much lift. You only need enough to get you, your gear, and your weights, to the surface and keep you there comfortably. Unless you're planning to dive doubles or are simply a huge person, you won't need something with more than 30-35 lbs of lift ... and probably somewhat less than that unless you're diving in cold water. Too much lift means bulk you don't need ... and that's just going to make you work harder in the water.
Jacket style? Back-inflate? Hybrid? Backplate? These are all valid choices that will be determined by the kind of diving you plan to do. A jacket style is probably what you used in OW class. It's easiest to keep you vertical on the surface, but underwater it's more difficult to learn good orientation (possible, mind you ... just not as easy). A back-inflate is the reverse ... it tends to want to push you face-forward on the surface (something that's easy to learn how to overcome) ... but it's much easier to learn proper orientation underwater. The reason is due to where the air goes when you hit your inflator button. Hybrid models basically offer a jacket style with a small integrated wing ... they're a compromise on the advantages/disadvantages of each. Backplates are the high-end performers ... but many folks just don't need high-end performance. You have to decide what's important to you.
Weight integrated or not? The advantage to weight integrated is convenience and comfort. For the warm-water diver, it means no weight belt. For the cold-water diver, it means less weight on your hips, and a way to distribute your weights for optimal trim. One disadvantage is that a lot of lower-end BCDs rely on a simple velcro closure that, as the BCD ages, wears out. Then your breakaway pockets turn into fallaway pockets ... likely to come out when you don't intend them to ... and that can cause a runaway ascent if you don't react quickly enough to recover your weights at depth. If you choose to go with a weight integrated BCD, make sure you choose one that has a mechanical release system, rather than just a velcro closure holding your weight pockets in place.
Padding ... many BCDs come with a lot of padding. It's comfortable, but it comes at a price. The more padding on a BCD, the more weight you're going to have to wear to sink it (padding floats). Also, consider that a BCD with a lot of padding is bulky, and that might matter if you plan to travel a lot. Generally speaking, unless you have a bad back or something, the less padding you get on your BCD the better off you'll be.
Hope that gives you some ideas about how to shop for a BCD ... I'm sure you'll get some other ideas as well ...
... Bob (Grateful Diver)
