Step 1. Disclaimer; Disclosure
First of all, keep in mind that nothing I say is etched in stone, or if it is, it shouldn't be. These are just some of the tricks I use, and everyone has their own methods. If anything I say doesn't ring true, then by all means, ignore it! There are stellar examples of quality songwriting which are exceptions to everything written here. For instance, the order of the steps is almost completely arbitrary; I've certainly written songs that didn't follow them. But I do suggest that you look at each step at some point in the process; I usually tend to notice things that could be improved in my songs when I look back
(see step #5).
Also, google "songwriting tips" and you'll have tons more to read, and probably of much better quality.
Here is where I'm "coming from" when it comes to songwriting:
I play guitar and write and sing. I believe that quality in songwriting lies in achieving a balance between (forgive the cliches) the heart and the head. Your inspiration comes from your guts; from emotion, and you render that raw emotion "deliverable" by filtering it through your brain. If the balance is off, the song is less than it could be. Pure emotion doesn't translate to the audience unless the performer (or songwriter), intentionally or unconsciously, makes that emotion accessible.
Hendrix's axe was a part of him, his emotion translates ... but what if he just hadn't practiced enough? Or he hadn't invested lots of time playing with new hardware, new sounds? Or if he forgot all of the words (Yeah yeah, I know... he DID forget the words a lot)? My point is, he was able to convey the emotion (guts) of his music, because he found a way to make it work on stage (brain). Jimi (at his best) found a balance, and for him it happened to be a bit farther toward the guts than the head.
Sting has done some truly great songwriting, but he constantly writes songs with too much brain and not enough guts. Too much meditation? Not enough? You be the judge.
I do believe that there is great value in a song that a huge number of people like. "Popularity" is either a sign of a truly bad song, or a truly great one: There will always be an audience for cookie-cutter pop drivel, but there will also always be an audience for a great song. Anybody who has been at a performance where the whole audience knows the words and is singing along, has felt the value of a "popular" song, and it's elitist to suggest that the moment a song becomes popular, its quality decreases. So I think that the best songs have something about them that "lets everybody in," or at least, lots of folks, rather than focusing on an extremely narrow audience. Everybody appreciates a great song, regardless of the genre, and I think music is about communication. So I think a song that is well-written, is one that more people "grok."
As a songwriter, I try to write songs that "don't need me." By that I mean, I want them to be able to stand on their own, to be of sufficient quality that any decent singer could sing them. Few of the truly timeless, transformative classic songs have "weak spots" that a singer must "sing around." In my opinion, it is the songwriter's job to take their inspiration and wrap it in a package that magnifies; that enhances. A "poorly wrapped" song conveys little or none of its original magic, no matter how genuine the inspiration. And a song with no "guts" is just a wrapper.
The craft of songwriting is like cutting a gem.
Bad songwriting hides or distracts from the inspiration, good songwriting amplifies it without overpowering it.
That being said, "Louie Louie" it a great song... so again, take what I say with a grain of salt.