How do I remove labels from glass jars/bottles?
There usually two different kinds of glue you commonly find. 

One will come off if you just soak the label under water over night. Doesn't have to be soapy. It helps to score the surface of the label with a cross hatching with a razor. Some labels are waterproof. You need the water to get through to the glue. 

The other kind of glue will come off with VM&amp;P Naphtha (common solvent at a hardware store) You can also use Ronsonol Lighter Fluid, which is basically the same thing, but a little bit more refined and clean. Both are far superior and cheaper than "Goo Gone" or "Goof Off". With Naphtha you pour a liberal amount at the edge of a sticker. Use a plastic scraper to get under the edge of the label. As you lift the Naphtha will be able to get under the label and loosen more of the glue. Keep adding more Naphtha. Peel slowly. Let the solvent glide the sticker off. Don't force it. Naphtha has a strong smell, but it evaporates quickly leaving no odor. It can be used to remove stickers from paper. 

If you are removing a sticker from something valuable then I would use the Ronsonol Lighter Fluid. It almost exactly the same stuff as VM&amp;P Naphtha but it's refined to be a little cleaner and less smelly (after all, it's designed to sit in a wick lighter in your pocket). Some people blanch at the idea of dumping lighter fluid on a book to remove a sticker, but after a few minutes the fluid will be gone. Test first. Only very rarely have I found that the lighter fluid will dissolve ink or paint. It's actually pretty neat how well it targets sticker glue without harming anything else.