[jseliger]

Awareness, which may be one step above "Schlep Blindness:" http://paulgraham.com/schlep.html . Cultivate it.

In addition, read some and try to become aware of what others need and what others are working on.

Finally, when you become aware of problems or ideas, write them down. I'm a fan of small notebooks; other people use phones or computers or whatever. Look over whatever notes you've taken once a month, and once a year; look for patterns in those.