1) Comment your code profusely. If someone has to spend a lot of time studying uncommented code in order to figure out how it works, when he could alternately get the gist more quickly by reading good comments, then he’s more likely to throw up his hands and say “This isn’t worth my time”. This is true especially if the developer isn’t being paid to work on the code.

Uncommented code is developer-unfriendly.

2) Spend as much time writing good docs as you do writing code. Again, good docs give an “outside developer” a head start at working on the code.

The real reason a lot of open source projects wane and are abandoned is because the guy who originally wrote the source gets tired of working on it, and yet he has so poorly documented and commented the code that no one else (who may take over development) wants to spend the time getting up to speed with all this code. So new developers instead start their own projects, often unaware that they’re duplicating the previous efforts of others, and to make matters worse, these new developers perpetuate this situation by also writing uncommented code devoid of any good documentation.