Separate motion from contact
Syncopation places emphasis where a listener may not expect the strongest attack, often between the main beats. Your hand can still move in a regular down and up cycle while only some movements touch the strings. Mute the strings and count one and two and three and four and. Let down movements align with the numbered beats and up movements with the spoken ands. Keep the motion small and loose enough that silent movements are as steady as the sounding ones.
Make one offbeat audible
Sound a downstroke on beat one and an upstroke on the and after beat two. Leave the other motions silent while continuing the count. Repeat until the offbeat no longer pulls the next beat early. Add a chord only when the muted rhythm is stable. If the chord should sustain across beat three, allow it to ring instead of striking again automatically. The silence of a new attack is part of the pattern even though the strings may still be vibrating from the previous stroke.
Coordinate an anticipated change
Some songs move to the next chord just before a strong beat. Practice one such change slowly with a verified chart and compare it with the recording. Decide whether the harmony really anticipates the beat or whether only the bass or percussion does so. Move the fretting hand early enough for the intended upstroke, then keep counting through the following downbeat. Record a short attempt and tap along while listening. If the pulse remains clear without you explaining the count, the syncopation is becoming part of the groove rather than an interruption to it.