Open your multitrack recording in your mixing environment of choice. Usually, this will be a software digital audio environment such as Logic or Mixcraft. These applications were designed to mirror hardware-mixing environments, so if you are using hardware, the terminology will be the same. Engage all tracks that will appear in the final mix.
Press "Play." Watch the level indicators on the mixing board as the song plays through. Look for clipping on all tracks. "Clipping" is when a given track's outgoing signal exceeds zero decibels (dB), creating distortion or other unwanted artifacts. Note down any tracks that clip at any point as the track plays through. Note how much they clip -- this will usually be indicated in dB somewhere on the track's channel strip.
Listen to the song all the way through again. Adjust the volume downward in small increments on tracks that showed clipping on the first play-through. This may get rid of the clipping, but it may also reduce in volume the parts of the track that do not clip. If the overall volume is too low, quiet parts of the track will be lost in the mix. On those tracks, you will need to use a limiter.
Mute all but the tracks that need limiting. Tracks that need limiting will usually be drums, acoustic instruments and vocalists -- any sound with strong dynamic contrasts. With vocals and drums, it is usually best to use a compressor for more comprehensive dynamic leveling, but a limiter can be used in any case to eliminate clipping.
Insert a limiter -- software plug-in or hardware -- into each problematic track. It is important that the limiter is placed last in the signal chain for each track, after any effects, EQ or other processors. It must process the entire signal as heard at the final output. Limiters vary, but each will have at least a "Threshold" knob or slider and an "Output" knob or slider. "Threshold" sets the level in dBs to which the track's output will be limited, and "Output" sets the track's level in dBs post-limiting.
Review your notes for each problematic track. Earlier, you noted how much in dBs each track clipped. This number represents roughly the amount of limiting that should take place on that track. For example, if a track clipped by 2dBs over zero, set the "Threshold" to -2dB as a starting point. Do this for each problematic track.
Press "Play." Watch the level indicators on the limited tracks. They should show minimal, if any, clipping. On those tracks that still show clipping, reduce the limiter's threshold downward in small increments until the clipping stops. If any of the limited tracks need a boost in overall volume, adjust the limiter's "Output" parameter upward in small increments until satisfied with the way the track sits in the overall mix.