I'd like to propose a perhaps controversial idea: that creativity, such as composing a song or writing a story, can be improved by artificially limiting your artistic freedom. Not only will your task be easier if you ignore any debilitating and often trivial decisions in favour of actually getting something done, but your entertainment will be more palatable to the average person as a result of fitting within accepted constraints.
Some people will argue that true art should be unhindered, of course. Maybe they're right, but I for one am trying to create things that people will simply enjoy, rather than ponder. If you're trying to elevate the human spirit, you should probably throw away this essay right now. If, however, you're trying to write a song or story that you want to be popular, but you're stuck because you just don't know where to begin, you might benefit from my advice.
We can sometimes be overwhelmed by choices. For instance, you can write a story in any genre, set in any time period, using first or third person narration, and past or present tense. The list goes on. Similarly, you can write a song in any key, using any instruments, tempo, time signature and style.
Some of these are trivial, unimportant decisions, but they must still be made before you can set pen to paper. The first thing that can help is to realise that these decisions are stalling you and, in the case of the trivial ones, to simply pick one thing or the other. Making the right choice isn't always as important as making a decision at all and then moving on. Don't be afraid to get it wrong the first time. Rewriting a story from a different character's point of view is more fun than spending all day thinking you'll never make it as a writer. Transposing a song into a different key is more fun than halfheartedly tapping the odd note on a keyboard in frustration for an hour.
It's OK if the first draft is terrible. You can rewrite it as many times as you like until it's great. What's important is writing it right now.
Have you ever read a guide that recommended telling a story with a certain title or depicting a certain event? Was it easier to write within that self imposed constraint? You can pick any such constraint yourself, just to have a starting point. Write a set of short stories, each one named after a song from your favourite album. Write twelve songs, one in each major key.
Now here's the advice that will likely get me lynched by artists trying to break out of the mould and try something new: if you're going to use constraints anyway, why pick arbitrary ones? There's a whole bunch of ways to limit your creativity that will simultaneously make your finished product more accessible to most people.
For example, if you know where your story should start and end, then great, start writing it. If not, you could try starting it at the first interesting part — a murder, something that appears physically impossible, falling in love with someone unattainable, or so on — then raising the tension to a climax. Trying to end each scene or chapter on a cliffhanger can also be a fun challenge that simultaneously makes the story more gripping. If you're completely stuck for something to write about, a book like Ronald Tobias's guide Twenty Master Plots can be handy just to give you a template you can start with, simply because writing about anything that takes your fancy can seem more daunting than writing a forbidden love story or a simple revenge story.
Similarly, if you've worked out an arrangement for your song, then great, go with it. If, on the other hand, you've spent a while trying to choose between writing an AAA format lyric or an AABA format lyric, not to mention whether you should have a ripping guitar solo or not, then try the ubiquitous lyric format of two verses and a chorus, coupling it with the corresponding musical arrangement of intro, first verse, chorus, second verse, chorus, bridge (this is where that guitar solo or breakdown goes), chorus, chorus, outro. The KLF's tongue-in-cheek guide The Manual expands on this idea very well. My point is that if you've resigned yourself to quickly picking an arbitrary arrangement anyway for the sake of getting that particular decision out of the way, you might as well go with one that's likely to make your song more accessible.
Don't get me wrong — I'm not by any means suggesting that you always seek out a rigid set of rules before trying to create something. If you're already stuck, however, you might find that setting one or two limits allows you to focus on what really matters: the specific characters and conflicts; the melodies and rhythms. If you work out what's important and what isn't, you should find it much easier to focus on the details that really bring out your own unique style.