Write less code.

Banish Not-Invented-Here and make good use of existing libraries/frameworks/toolkits to provide common (and generally non-defining) functionality so that you only need to write what's new. For the parts that you do need to write yourself, build them with re-use in mind so that you won't have to write them again for the next project.

Even if you don't increase the number of lines of working code you produce per day, you can still get more done in less time by making each line do more.