The following is my first game on KGS; I appreciate any suggestions as to how I can improve my play.

My intuition regarding the game I played is that I lost it in the moves following 126 when I was unable to secure the upper section of the board.

Prior to this I've played games against the AIs and read beginner articles on general principles; I haven't learned any particular joseki, fuseki, or other patterns.

Three things while waiting for Bill :
1. You don't need to close your territories so soon (ex: moves 9 & 11, and many times later on)
2. Try to avoid making two weak groups too close from each other (ex: move 13. Your right one still needs some care)
3. Don't squeeze the toothpaste : http://senseis.xmp.net/?SqueezingOutTheToothpaste
(ex: moves 81 to 100)

Hope this helps ; welcome to the forums and the game!

A few ideas:

Thank you both very much for your advice! I really appreciate the effort you spent looking through a newbie's game.

It does look like the toothpaste squeeze at 81 lost me the upper region.

Ed points out Q6 (and later O4) as vital points; is there a reference I could read to understand how he diagnoses these locations?

For what it's worth, I found the reasoning behind Ed's vital points here:
http://senseis.xmp.net/?DiagonalAttachmentFollowUp