You have a lot of great tips here. I can think of a couple that haven't been said in quite the same way....
Just a pinch of salt will lift the flavor of any dish (even desserts) especially where it isn't called for. Don't add it at the end, but during the mixing.
A propos of mise en place: 1. I always suggest to my students that they invest in a few medium sized trays for gathering the mise en place. Put all the ingredients for each dish you are preparing on a separate tray. It eliminates a lot of confusion when you are making multiple dishes at the same time.
2. Chop your mirepoix ahead of time, if you can, and make extra of each ingredient and bag that for future use. Chopped onions, celery, carrots, peppers all freeze well, so if you won't need them right away, just pop them in your freezer door. You'll be glad you did.
When assembling dishes like Lasagna, never make just one. It's just as easy to make two. You then can freeze #2 and have a meal made ahead for "you never know!"
Oh! and don't wash good cookware (or you knives) in the dishwasher!