I've always objected to use of the words "amateur" and "professional" when describing writers. In the workshops I've done, I've always used the terms "aspiring" and "established". In my years of writing for a living, I've encountered some extremely professional "aspiring" writers, and to this day suffer very amateurish "professionals".

Every established writer I know has pretty much had the same experience - write a lot of songs to get a few cut. Since I've been in Nashville, I've had somewhere between 3,000-4,000 songs published, but just somewhere in the vicinity of 200 cuts. The hit-to-miss ratio is high, even among established writers, at least the ones who have been doing it a while.

The current business model of writing with the artist/producer/etc. has improved that disparity dramatically, but it's dependent on the writer being in the right clique or circle to get in the right rooms to make that happen.

As for ideas, I put every idea I get, good or bad, on the notepad on my iPhone. The list is pages and pages long, but every day when I sit down to try to write, I scroll through them. More often than not, I'll stumble across some idea I had months or even years ago that suddenly "clicks", and I know how to write it (the disclaimer here is that I begin with a title, so I start lyrically for the most part - on occasion I'll stumble onto something melodic that I will then write to).

http://www.rogerbrownsongs.com
http://www.nashvillesongwriters.com/roger-brown