Ground

First off - the most important element of any Antenna System is the Ground.
I have walked into interviews and said, "Without you even telling me anything about your product, I can tell you that you probably have grounding problems" and get knowing knods of heads.

Ground is a large polished continuous piece of highly conductive metal of reasonable thickness, atleast one wavelength in Radias with the antenna situated in the middle. Anything less than this is a compromised ground which means imperfect antenna propogation patterns, uneven gain distribution, and possible center frequency shift.

A wire is not a microwave ground or even an RF ground. A ground should be unbroken, however the reality is that we often get a corner of an over populated RF/Digital pc board with no regard for the antennas function. In this case try to place the antenna as close to the middle of the board as possible and away from other tall components. (Note: some antennas will only work on the edge of the board.)