For those that do not want to the effort to create a true Yagi antennae we found this two articles on creating a Cantennae, essentially a tin card cut to the appropriate length. The key is cut the length to 1/4 wave, half wave or full wave of the main carrier frequency of the signal you are trying to detect.
Cantennae construction basic:
Wireless 2.4 GHz Directional Antenna Calculator
Enter the can diameter and get the length of where to place the pick to detect the peak of the standing wave. from the end of the can.