Learn what the seven bands control before beginning to set your equalizer. Most seven-band equalizers have a 60Hz band, a 150Hz band, a 400Hz band, a 1 kHz band, a 2.4 kHz band, a 6 kHz band and a 15 kHz band. These bands move from low frequency to high frequency, with 60Hz representing the very low end of the spectrum and 15 kHz representing the extremely high end of the spectrum.
Try to decrease frequencies to achieve the sound that you want instead of increasing them. Increasing a frequency can often cause distortion or unnatural sound, while decreasing a different frequency may have the same relative effect on the source material. For example, if you want to hear more mid-range sounds in the recording you are listening to, it may be preferable to reduce or cut the 60Hz and 150Hz band in the low end, and the 15 kHz and 6 kHz band in the high end. This will make the mid-range more present in the recording being listened to.
Check to make sure you have not created any distortion after equalizing the audio. While most distortion is only a concern if it is audible, distortion can be present when it cannot be heard. Many equalizers have a volume output meter on the front panel display that will show you the volume of the audio as it is received, and how it is output through the equalizer.
Listen to a wide variety of music in the space you are in to see if you encounter general problems. For example, many rooms with a square shape tend to have an excessive bass buildup, and a reduction of the 60Hz frequency is generally sufficient to reduce the buildup. Always diagnose the problem of your particular room before making rash changes that may make listening less pleasant.