1. Spend more time
This might be very obvious, but spending more time on a composition is likely to make it better. Do not not try to finish it, but instead aim to be happy with every piece and every aspect of it. When I think I finished a piece, I will let it rest for a few days and come back to it again, often noting quite obvious things to change.
2. Re-do and re-start
My own song writing process used to be quite linear: Starting with an idea (a short piece on the piano most of the time), find an interesting combination of sounds, add a couple of more pieces, tweak, tweak some more, finished.
My design process, on the other hand, is much more complex: Starting with an idea and jotting it down very quickly, detail the drawing with the aim to get proportions and relations right, always finding some parts that are not working very well, trying to find out some other way of doing it, reducing the concept to the barest minimum to find out what the most important aspects are, work on something else, going back to find that 80 % of what I had wasn't good, approaching the whole idea from another perspective, and so on. Re-doing and re-starting are essential to working through a design project and I think it is for music creation too. The different perspectives you get on your idea and the material gives a much fuller understanding of the problems you are facing, and with every new try it will probably get closer to a solution you are happy with. It takes more time, but the outcome is often much improved.
When I started to apply a more non-linear composing process, I quickly ended up with a lot of material not being used in projects. Sometimes because it wasn't very good, but often because it just didn't fit the context. That meant I had plenty of ideas to go through when I was starting my next project. Not having to start from scratch every time feels so much easier, and the time spent on a project can be reduced or more time spent on detailing or exploration. It's like I have added a whole new level to my creative process, where creation is contantly going on, and I can pick song ideas from it whenever I need or want.
It also means I can finish a song, throw away everything but an exceptionally cool sounding bridge, and use only that as a starting point for a new piece. Completely without feeling bad about it, as the other parts of the song may very well continue their lives in other songs instead.
4. Be a good critic during the process
The ideas presented above point to one important role for myself: I need to be a good critic of my work. Not shying away from saying a song isn't good, as equally important, is not to put any accusation or devaluation in the critique. Simply state that 'This is not the result I intended, so I will try to change things till I'm happy'. It's so easy to make the mistake of judging something as not good, when it's not been worked through.
Here are also some advice that I think are important in the long run. Study theory and ignore most of it. I know more about color theory than I care to admit. I'm aware of it when I work with design projects, but breaking some of the myriad "rules" is common practice. Listen to other people's music with a pen in your hand. Listen thoroughly, several times, and write down everything you can: Song structure, what instruments go where, bpm, scale, chord progression and so on. The more theory you learn, the more you will be able to identify. Read up on/listen to history of music. So much to learn there... Daydream. This is, I think, the undisputable master of all creative techniques.
And what does the future hold for my composing? What parts of my design process haven't been ported yet? One of the concepts I'm looking forward to trying, is making quick sketches in early mid-project, and take one specific aspect as far as possible and see where it leads me. In a design process it is often very rewarding, not because you end up using the result straight off, but because you learn so much about the project, and some of the results are bound to be quite unconventional. And with a slight rework, parts of it can often be used in the final project. It can also revitalise that higher level of creativity, giving you a feeling of a creative process that is a living thing, constantly evolving. And isn't that what most of us want?
You can see my design projects at www.blendadesign.com
Listen to more of my music at www.soundcloud.com/imifal