the results are subtle yet really beautiful. I've also experimented with different colors of glass which also provide a neat effect - light blue in particular
To start you'll want to buy some glass etching cream..I've found Armour Etch to be the best leaving the nicest finish , but there are many brands out there that you can try - even leaving different finishes such as silver or gold glitter varieties from "Plaid" But I think simple is better and have found those to not leave as great an imprint as the Armour Etch.
Next you'll want to get a stencil, or other type of sticky design maker - masking tape works great for lines, hole punch protectors work great for polka dots, and there are all kinds of specially made stencils just for glass etching which are re-usable as opposed to a sticker which is only good for one use. For my project I used these alphabet stickers - using their outline as a stencil.
Next just place the stencil on the glass where you want your design - remember it is the hollow of the design that you'll want to etch or inside.
Then just take a brush and fill in the space left by the stencil - leave on for 10 minutes and remove the stencil - and voilà - you're left with a beautiful personalized gift.
These glasses are a present for a friend with the initials N.F. - let's hope he likes them.