Categorize your records by genre and BPM (beats per minute). When mixing, it is easiest to stick to the same genre and songs of similar BPM.
Select two records of the same genre and similar BPM. Place one record on each of the turntables. Ensure volume levels are set on the mixer to play both decks, the headphone controls on the mixer are set to "cue," and the crossfader is slid all the way to the side that would play the deck you intend to start the mix with.
Start the turntable with the record of the first song you wish to play. Count out the beats. Rhythm is best counted out by tapping your feet to the bass kick of the music. For most music, this will be in measures of four, with a change every eight measures.
Start the other turntable while listening to the output through the headphones. Keep one ear uncovered so you can hear the currently playing record on your speakers. Use the pitch fader on the turntable to speed up and slow down the record to match the beats.
Figure out the necessary pitch change by looking at the difference in BPM. For example, if the currently playing track is 126 BPM at 0 percent pitch change, and the one you want to mix to is 124 BPM at 0 percent pitch change, the percentage difference is 1.6 percent. Thus the pitch should be set as close to +1.6 percent pitch on the turntable with the record your mixing to ensure quicker beatmatching.
Set the pitch as necessary, following the directions as set above. Place your hand on the turntable to slow down the record, or push it slightly forward to assist in matching the beats of the two records together. When the bass beats blend together, the tracks are beatmatched.
Slide the crossfader to the center to play the synced tracks over your speakers. To fade out of the mix and completely to the next track, slide the crossfader to the opposite direction of where it started.