11:45 a.m. on January 28, 2004 (EST)
If you take up mountaineering, you will be poor. Especially if you are a gear freak (as many of us are).
Ummm, sorry. Better give a serious answer.
The best way to learn climbing is to find a willing mentor. The 1-week or 2-week quickie classes are ok for teaching skills, but they do not teach the most important part of being a mountaineer, namely judgment. Climbing for a couple years with a good mentor will start to give you that.
Hang out around your local climbing gym, and you can learn a lot of the basics of belaying, climbing moves, etc, and you can meet up with local climbers, some of whom may be willing to take you on. Keep in mind that gym climbing is not real climbing (they are, after all, artificial walls and artificial holds). So eventually you need to get on real rock.
Another thing is to go to the local bouldering areas and spend time chatting with the climbers. You do not need a lot of gear to start with. A harness and maybe a couple of carabiners and a belay device, at most. Shoes are nice, but you can use running shoes or hiking boots to start with. In fact, starting that way will teach you a lot more about using holds and various techniques like counterpressure than if you have the latest sticky-rubber specialty shoes. In other words, don't go out and buy the latest greatest gear right away. Climb with others enough to find out what you really need for your local area. Add gear appropriate for other areas when you go to the other areas, but not before.
The Sierra Club used to offer climbing classes, but the insurance changes killed that some years ago. There are sections that offer courses in backpacking, winter camping, and basic mountaineering, but technical climbing is not offered anymore (the only remaining Rock Climbing Sections are now social groups, although you can hook up with climbers at their meetings). The old RCS groups mostly split off to form independent clubs.
There are a number of independent clubs, some around for over a century. In the East, there is the Appalachian Mountain Club. In the Pacific Northwest, there is the Seattle Mountaineers, plus the Mazamas in Oregon. In between, the Iowa Mountaineers are long famous. In Southern California, there are several clubs, mostly former Sierra Club RCS groups.
Another place is to go to the local climbing store and ask the folks there (or the climbing section in EMS, REI, etc).
Yeah, you can take one of the 1 or 2 week quickies. They cost a lot, but they do introduce the basic skills. Afterward, you will still need to link up with experienced climbers to gain the needed experience and develop judgment.
But again, take it slow on the gear. Just get the basic harness, a locking carabiner (try to get one of the HMS style - designed to take a Munter hitch), and a belay device (ATC, for example, or any similar tube-type device). Decide on what part of mountaineering you want to pursue before you buy footgear. Rock climbing uses sticky-rubber slipper-like shoes (some are actually called slippers, others lace up). Snow and ice require a heavier boot that can take crampons, often a double plastic boot. Ski mountaineering takes yet another family of boots. So decide first, and you can rent in many cases before you buy.