It can be easy to slip into a songwriting routine. Keep your songs feeling fresh by abandoning the approach that you've previously used. The next time you sit down to write a song, do the opposite of what your instinct tells you to do. Use a word that doesn't rhyme, leave a blank space or use a minor chord where you'd normally use a major.
The chorus is the payoff in any song. It's the bit that we remember the most and it has the hook. There's no rule that says your audience must wait for the first verse to finish before the chorus. The Beatles song "She Loves You" starts with the chorus before moving into the first verse.
Start each song with one instrument, three chords and your lyrics. Find ways of arranging the chords or playing them differently to create interesting songs. "Wild Thing" by The Troggs only has four chords.
If your well of inspiration has run dry, find a new well. Early blues musicians took inspiration from the sound of the trains that passed them as they worked. They used their instruments to emulate the sound of the train's whistle. Listen to bird song, machinery or even the sound of your dinner cooking in the pan and emulate the sound on your instrument. The process of emulating something new will introduce new melodic and rhythmical ideas that you can take forward.
Every major chord has a relative minor and every minor chord has a relative major. A relative minor chord has a different harmonic structure, but exactly the same sharps as its relative major. For example, C Major follows the 1, 3, 5 harmonic structure and has the notes C, E, G. The relative minor is A Minor, which follows the 1, flat 3, 5 harmonic structure and has the notes A, C, E. Neither has any sharp notes and there are two notes in common. This makes the chords interchangeable. You can sing the same melody over A Minor and C Major without it clashing. But the harmonic structure is different, meaning the minor chord gives a more melancholy sound than the major chord. Swapping one chord for its relative is an effective way of adding lift to a chorus. Prince uses this trick on "Little Red Corvette." The verse chords, when played in the key of C, are C, D and E Minor. On the chorus, he swaps E Minor for the relative major (G Major) and leaves the other chords the same.