V. DRINKING WINE
You can tell a little about the wine even without opening it. Besides a moldy cork (see below), perhaps the "bottle fill level" known as ullage, is lower than you expect. If the bottle was low to begin with (I'm told not uncommon in some Italian wines), you don't have to worry about it. But there are other causes. If the wine has been subjected to high heat, the wine can expand and liquid may be forced out through the cork. Since heat isn't good for wine, this can be an indicator of problems to come. On the other hand, increase in ullage is natural over a long period of time and even can be a selling point at auctions. Other problems that could cause bottle leakage would be damaged corks or storage in a very low humidity environment, which can cause the corks to dry out.
Corks and Capsules
Most corks are made from cork. Since cork is expensive, some wineries are experimenting with making corks from plastic or other high-tech materials. Since the idea of the cork is to keep what's inside the bottle inside, and what's outside the bottle outside, it doesn't seem to matter what the cork is made of. It is questioned by some, however, whether a non-cork cork might allow the material it is made out of to leech into the wine with harmful side effects to the wine and to humans. A screwcap (gasp!) probably is better than a cork since it does the same job and can't "cork" the wine. Screwcaps are now coming on the market in somewhat more upscale wines (they've been on jugs for years--and don't forget that a lot of wine comes out of "milk carton" type cardboard containers that certainly don't have corks).
When you remove the "capsule" (the thing that covers the top of the bottle around about where the cork is, which may or may not be made from some sort of metal foil), you may find a cork which is discolored or even has a lush growth of moldgrowing on top. If whatever it is hasn't gotten into the wine (also check the "fill level"--if wine has leaked out it is a further indication of trouble), then all you need do is wipe the cork off with a damp rag, towel dry it a bit and remove the cork. Wipe off the top of the bottle. Also check out the article on "corked" wine. People also wipe off the top of the bottle in the hopes of removing anylead contamination from the foil on older bottles of wine. To the best of my knowledge, lead foil is no longer used. Since foil is merely decorative, some producers are dropping the foil altogether.
Sometimes you may see something that looks likeglass crystals on the bottom of the cork (or sometimes in the wine). Assuming no true contamination from the winery, these crystals are probably the result of tartaric acid in the form of potassium bitartrate(cream of tartar). While I don't vouch for accuracy of the information is this guide, I'm told that this is tasteless and harmless.
By the way, a handy use for leftover corks is to clean knives. Keeps your fingers away from the blade, but lets you exert enough pressure to get the blade clean.
There are lots of different types of devices which will remove a cork. Some are a lot easier than others. To me, one of the harder types is the one that is invariably used by the waiter in a restaurant. I once asked a waiter why he didn't use something easier and he told me that the manager thought it made the place look more "professional." The only benefit I can see from those sorts of corkscrews is that they are useful when pulling a cork from a bottle of wine that is sitting in a cradle (and they have a built in knife for cutting the capsule).
Some people don't like putting a hole into their cork (I guess they figure they're going to use it again?) and use a cork puller known as an "Ah-So". The device is made of two metal prongs which you wriggle back and forth so that the prongs move down the side of the cork (sometimes pushing the cork into the wine). When you hit bottom the tension lets you pull the cork back up. I don't find these types very effective.
There are expensive corkscrews, like the US $100+ Leverpull (tm)which works, as many times as I have seen it in operation (mostly in winery tasting rooms), quite well. (It is the sort of thing you would bolt to a countertop.) But I don't actually see why you need to spend the money on it. I've gotten pretty good at using the Napa motel free giveaway corkscrew (you can get them for about US $1). At home we like to use the approximately US $20 Leverpull (tm) which has a Teflon coated screw and a nice long mechanism that extends at a 180 degree angle at the top which you can push around with your finger when the mechanism is extended (to distinguish from a slightly less expensive model that you twist with your hand). Some people say "don't let the screw go through the bottom of the cork." It does with the Leverpull, but it does it so neatly there never are any particles that come loose (at least so far!).