My biggest help. Don't write songs in the studio. Too many distractions. Mind you, this used to be the general rule, when studio time cost hundreds of dollars an hour. Now days, everyone has a studio in their bedroom, and the concept has been lost.
I try to get to the basics of the song during the writing process. Makes it much easier to tell if you have a good product.
When I write in the studio, its on the rare occasion that I'll end up with a complete finished tune. Generally, I'll end up with a song fragment, which I swear I will get back to later, and that rarely ever happens.
Or, the other thing happens, and 5 minutes into the new song, something stops working as it should, (computer, instrument, Daw software, ect.) and I spend the rest of the evening chasing ghosts around the studio, with the song only a faded memory.
Nope, not any more. Now, I write songs on guitar or keyboard, away from the studio. Only when I have a complete song on paper, do I take it in the studio. This way, if the studio ghosts do appear, they only get my time, not my song.