Create musical tension by writing a melody over a chord or progression and then sing it over a different one. It will push you into new melodic territory.
A Day In The Life (verse – I just had to laugh)
I Want To Hold You Hand (bridge - and when I touch you)
Frank Zappa used a variation of this technique by literally taking the solo from one live song and overdubbing it onto completely different song. He called this approach Xenocrony or “the Ampex guitar”
Ticket 13: Make The Vocals Stay On Non-Chord Tones
Ticket 14: Write An In-Key Melody Over Out-Of-Key Chords
Ticket 27: Place Your Main Lyric On The Highest Point Of The Melody
See the full list of songwriting tips here - Tickets To Write