You must synchronize the speed of your two songs before crossfading from one turntable deck to the other. Line the tracks up so that the drums play at the same time if possible. Use the rotation speed selector and pitch adjust knob to speed up or slow down your songs as necessary if they do not synchronize naturally. Find the right rotation speed for your record and fine tune the pitch adjust until the drums, bass, or melody line up as desired.
Nudging is a more extreme means of synchronizing songs that do not line up perfectly regardless of speed adjustment. Nudge the record forward or backward in time every bar or measure to synchronize the tempo of important in-song timekeeping indicators like snare drums, bass drums and hi-hats.
Samples may also cover up synchronization miscues. Record a small portion of the song you are playing to fill in time lapses if you own a mixer that captures and plays samples. Such samples may also be used as effects to layer on top of your original song to create an original audio treat for your listeners.
Spinback involves playing a song on one deck and manually rewinding it while crossfading to a similarly timed song on the opposite deck to finish a bar or measure. This is often used as a reparative tactic for a blend that does not finish cleanly. While you switch to the other song, quickly wheel the first song back to your original play point. Repeat these steps as necessary until you're ready to move on to a new song or mix.
The dead stop and power cut are similar techniques that provide spontaneity for the introduction to a new track. The dead stop is exactly as it sounds. Hit the stop button on your deck for a sudden stop in your first song instead and slide the crossfader immediately to the other deck to pick up in time with a mutual first beat. For a power cut, turn off the first deck's power for a slow, gradual stop. Then, switch to the second deck in time with what would be a mutual first beat.