Oxygen is number one, of course. Be very aware of your oxygen supply and flow.
Be very aware that you're playing with fire at those altitudes. O2 stops, you don't have much time with useful consciousness. Are you prepared to make an emergency descent of 5000' or so in a minute without taking the aircraft past Vne?
Calculate time to climb from your POH. Also calculate distance. It's going to take a long time and a lot of gas to get up there. You're also going to cover a lot of ground.
After that, calculate a reasonable descent. Something 1000'/min or lower to take it easy on your ears.
Tahoe shouldn't be a problem. Do a density altitude calculation though and run all the other numbers from it. It's mountain flying.
If you depart south, can you climb straight out and clear the rocks, or will you have to circle in the valley to gain altitude? What's your navigation plan? What direction is lower terrain? Stuff to think about.
Leaning is what we do here for every flight. Check your POH for high altitude leaning. Most Cessnas will say lean for maximum power at full throttle above 6500' DA.
Full throttle run-ups are hard on props when they suck up crud, so the usual procedure here unless you know you need every last ounce of engine power is to lean to peak during the run-up (lower RPM than full power) and then twist the mixture two half-turns in.
If its warm out, you'll likely be doing the equivalent of a takeoff at 7500-8500' DA easily higher.
Calculate takeoff distance and then note a runway marking or landmark that will tell you if the airplane is really performing to spec and realize it'll feel like a long long roll.
Let it roll and keep accelerating. It takes a lot of air molecules going over that wing to lift yer butt, and there aren't as many of them up there.
If you pass your spot and the aircraft isn't performing right, stop. Remember you have basically go-kart brakes and they're going to get hot. Get slowed up but don't lock a tire. You are rolling much faster over the ground than usual.
(Note: This applies to your arrival landing too. Just roll out. And groundspeed will look faster. Nail your approach speed with the ASI and don't slow the view out the window down much to try to make it look like a landing at home. ASI is key. Don't try to stop the thing in distances that seem normal at sea level. Again, do the POH calculation for landing distance using the DA temperature at your expected time of arrival. Look at a weather forecast that has "hour by hour" temperatures online for the day and use the hotter one if you're arriving in the half hour.)
Then lift off at the appropriate indicated airspeed. Don't "pad" it. The ASI is seeing the right number of air molecules crammed down the pitot tube.
Try to arrive/depart when it's cool. Even small temperature changes make a significant difference in DA.
As someone mentioned, climb will be slow. A go-around can sucker you into pulling too hard... Just pull to set Vy (or Vx) AMD trim it. Give it time and distance to climb. Look up the change in Vx for altitude.
Don't forget to turn the O2 off when you don't need it. Gets spendy pumping O2 into the cabin that you don't need. Flip side, make sure the O2 is flowing before you need it on the way up.
But trust me, that's not the problem.
