Dita, I guess it depends on what you consider a good song vs. a poor song. I agree that there are more poorly-written songs out there than really good ones but very often those poorly-written things actually become hits. So what do I know. I get really excited when I hear what I consider a well-written song on the radio, which is not very often.
My best songs just fall from the sky. If I have to force it, I step back a little, and just let it flow. I write anywhere and everywhere and nowadays I have blank paper in my Daytimer for that very purpose.
An old friend, who is writing songs just for fun, called me the other day and said, you wanna work on a project? They guy I'm working with isn't on the same wavelength as me. Sure, I said. So I went over there last night. Sure enough, he was a nice enough guy, and enthusiastic about writing, but he's into "oh this has to go by this formula and has to rhyme every other line" and friends, lemme tellya, I Don't Buy That. I never have. Generally speaking, I do rhyme, but I don't think a song has to rhyme to be good, and I don't think it has to follow any set formula.
I heard an interview with Tom T. Hall one time, and he said his best advice to writers was to write what they felt, because people can tell when you're writing for a specific market. The "market" songs don't have the same feel as songs that are written sincerely. And I guess he would know.