I write my own lyrics and phrases when I get inspired by other songs and music.
Example:

I listen to a cool song and I come up with my own lyrics.

Also:
Write everything that comes in your mind on a notepad,

You can also think of a life experience you had in the past that has touched you and write based on that

Try not to make your lyrics ordinary...

Read also some poetry...listen to songs you like and get inspiration from them.