Sticker design can be a gratifying or frustrating experience, depending on how you approach it. The first step is to know what the sticker or label is being applied to. If its a 500 ml round bottle, then take a measuring tape and measure for the fit you want. That's your basic sticker size. The sticker size should ideally not be set in stone, but you have a good idea of the parameters (some sticker sizes are critical, but we are talking in generalizations here). Next, you have to decide on the shape of the sticker. After these two basic steps, you need to know what information and graphics need to go on the sticker. You might find that the round sticker you originally wanted can't handle the amount of information you need on it. Also, your logo might work better with a rectangular or custom shaped sticker. Some designers crowd information into the sticker and some prefer a simpler, minimalistic label design. So the basic design steps are:
Measure sticker size (length x width) - this means measuring the "retail' or 'advertising" space on your packaging the sticker needs to occupy.
Decide on the sticker shape.
Check that you have allowed enough space on the sticker for your logo and information to fit.
Determine whether the sticker shape and your company logo shape are a compatible or good fit - for example, if your logo is rectangular (long and narrow) but you want a good fit on a square or round sticker. The opposite also holds true; you have a square or round logo but want it to fit perfectly in a rectangular sticker. Think about what is actually possible with what you have and the sticker or label you want.