Skinned up about 3000' vertical for.my first skin today. Holy fucking shit it's tiring. the snow was crust On 2' powder, the riding was tough. The skinning was awesome. My sparks afterburner were very easy to use but I lost a screw somewhere along the.line. The board is nowhere near as responsive as what I'm used to.
weight your steps on your heel, not the balls of your feet - especially important the steeper it gets.
something that can help this as well as general leg fatigue while skinning is to concentrate on lifting your weight from each step with your butt muscles instead of your quad/calf. you have to consciously think about it while you're hiking at first but it helps in the long run.
learn switchbacking and kickturns.
use your inside edges; when skinning up most people switch board halves so that the sidecut edges are to the inside of your feet...
bring your split crampons for when it gets firm.
learn when to say fuck it and bootpack.
edit: focus on breathing;
try and start at a pace you can keep - don't burn yourself out right out of the parking lot.
When I got to 35-45 degree slopes it was a challenge with slippage but I learned really fast to keep my weighted ski fully weighted and make quick switches of weight to avoid slipping. Fortunately I was with an experienced Tele skier that gave me some tips. I think my fatigue made the ride down so much worse.