Fill them with colors to make them bright: For all art, you need to create a base to get started, which can be drawing in case of paintings or preparing the clay when it comes to pottery. The same way you need to prepare your glass bottles for art, by filling them with some color or the other. It is best to go with good quality oil paints in order to achieve this effect. Water colors or acrylic colors can also be used in case you feel the shade and color effects that you need come in these medium only.
Add some artistic touches on the outside: The use of beads, spangles, stars, conches, shells, and other touches can be added to the outside. You will find that once you get started, it becomes much easier to come up with many types of embellishments that can be used.
Try to convert them into something else: The thing is since bottles have a transparency to them, they can be used to make them into a flowerpot or a lamp or in any other form depending on the shape or the size of the bottle. You can actually use bottles to make some sort of a chandelier if you put your mind to it. However, it needs a lot of creative thought as well as a lot of effort.
Advanced art will take more effort: In some cases, bottle art is created by cutting the bottle lengthwise and sticking two different bottles. You can so cut the bottle in half breadthwise and stick two different shapes to make an artwork that is modern in look.
The thing is art using bottles is something that even someone who is not an expert artist can do and that too without much in terms of expenses. It is almost as if you are recycling something that has no further use in your household to create something that is just going to be thrown out. And if you get really good at it, then you can even think of selling some of the pieces that you create.