MrDo0m

Do you tab out your songs? That always helps me because I can go back to whatever idea I had before when I have another moment of inspiration.

If you came up with a cool lick that you wanted to use for a different song.. maybe you could transpose it to the key of the original song you had? Who knows, it might work. And before someone goes on a tirade and says this is a terrible method of songwriting, it also might not work, but it's worth a shot.

Sometimes it helps to come up with a simple bassline, tab it out, and then come up with the guitar and drum parts over top of it, then come back to the bassline and expand on that.

It'll take some time no matter what, though.