Use this spinner wheel to get a song key. Writing songs in different key help build diversity and stimulate new song ideas
The best way to improve your songwriting ability is to constantly and persistently study what hit songwriters do. Learn from the best. Listen to the radio and take notes on what hit songs have in common. What is their structure like? Do they end verses on major or minor chords? Do they have a bridge? How many bars are in the intro? Try to figure out what the hit songs in your genre have in common.