The pictures are helpful.
Faster, Flatter Mattress Stitch
Easy to do and looks nice when done.
Yarn Overs for Different Situations
How to Improve the Loose Knit Stitch Before a Purl
I could have used this a long time ago!
http://artemiswolf.blogspot.co.uk/2015/06/photo-tutorial-how-to-improve-loose.html
Yarn Crafts 4 Lefties
Bill Souza has a lot of knitting tutorials for left handed knitters. I checked some out and they look pretty good.