Since it was already stated that even if everyone became a registered organ donor that would not solve the issue since there would still not be sufficient numbers (not enough people die in the required manner), I believe the real solution is through networking.  For example, if I needed a kidney and my brother offered to donate his, we would go get tested to see if we are a match.  He might not be a match.  However he may match someone else on the kidney waiting list.  That other patient may also have a willing non-matching potential donor relative/friend.  That person could possibly be a match for me, and essentially we could trade our donors.   Usually it would not be as easy as two people swtching, but when you have many people pooled together, many matches can be found.  This domino-donation concept is already in pratice as seen in this article.

http://www.medpagetoday.com/Surgery/Transplantation/tb/4567