If you're a perfectionist, placing your new labels on your bottles can be an exercise in frustration: you paid for those beautiful labels and neckers, but just can't get the things on straight. Here's a method I've developed that makes it easy.
Nearly every bottle I've handled has somewhere on it a very fine vertical seam, probably left over from the bottle mould. This makes a pretty good guide for perfectly aligning your label.
I first remove my label from the liner, and fold it mid-way and inwards so that the sticky side is facing out. The idea is to put an up-and-down crease directly in the middle of your label. Don't worry about creasing up your labels: once you apply the label, the crease pretty much disappears. Clean hands help for this, since you'll be touching the sticky side of the label, and I've found getting dirt on the sticky side can reduce the label's adhesiveness.
Next, find the seam on the bottle, and carefully apply the label so that the seam and your crease match up. Use the crease and seam as your guide to position the label into place. It helps to lay the bottle on its side during this part and to have a good amount of light to find the seam.
With the label in place, press firmly and run your finger down the crease to flatten it out. Then press down along the rest of the label to adhere it to the bottle.