I have always been intrigued about crafting using glass bottles. The results look so cool, but it seems really difficult to actually cut the bottles in a usable way. I did some research and found that this $17 device is the best way to do it (I got mine on Amazon).
Diamond Tech Crafts G2 Bottle Cutter
It takes a second to put things together but once it is together, it works great! You use this main device to score the bottles and then with a pot of boiling water and a tub of ice water, move the bottle (submerging the score line) from one pot to the next. The quick temperature change turns the score mark into a nice clean cut.
After that all you need to do is sand down the edges. Start with coarse sand paper and move to fine sandpaper. Only a few minutes of sanding is enough. I'll follow this post with others on the various projects I've used these bottles in!