If below 75% power full power run up and max RPM or First Cyl to peak EGT (and enrich slightly for smooth operations. No EGT lean to roughness than enrich for smooth operation.
For fixed pitch prop MAX RPM and enrich slightly.
Watch this video from Rod Machado. Link is queued to where he gets into technique. Recommend your go to start of video
https://www.youtube.com/watch?v=eBUfWI4C6sE&t=258s
This is what Lycoming says to with your normally asperated dinosaur juice to thrust conversion machine.
https://www.lycoming.com/sites/default/files/Fuel Mixture Leaning Procedures.pdf
KGJT ?
Carbureted ?
Fixed or Constant Speed Prop ?
EGT gauge or gauges ?
Fuel Flow gauge with table calibrated in % power ?
I'll assume YES, YES, CS, EGT all jugs, NO calibrated FF to DA % Pwr Chart
So full power, first to peak is the lean setting for about max power. Personally I enrich 100-150F from peak.
I typically don't do full power runups on the ramp/runup area which can pick up rocks and ding the prop. Also it is mostly likely hot and static full power runups will get your engine cooking under the cowl. Not really great. especially for Carb'ed planes (vapor lock). I will lean approximately for DA and then make adjustments on roll. My Approx lean starting point is during runup (2000 RPM typically but may bump it up to 2100 to 2200 RPM), ignition L&R check, prop cycle, carb heat/alt air check, lean to where I see EGT starts to rise. Tank selected as desired boot pump on. I adjust the mixture on the roll. You can also use engine sound and feel.
Most certified GA airplane AFM/POH have recommended technique to lean for high altitude departure. If you don't have high DA leaning for takeoff in your POH, consider adding it. Do you have takeoff distance and climb rates at different weights and DA's in your POH? Fuel Flow (FF) can be used to determine power vs DA vs Pwr. It requires you make a chart or table.
KGJT is just under 5000 ft elevation seen a 85 degree day this year already. DA = + 8000 ft very possible summer time. So that is about 75% power. Therefore leaning for maximum power is needed. Aggressively leaning above 75% power could cause detonation and engine damage or failure.
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KGHT has a 10,000 ft Rwy and a 5,000 ft Rwy. Take off is not an issue. However what about departure climb, enroute climb out and enroute planning? High winds in mountains areas is a different story than the flat lands. If they are high at surface or at altitude it can create severe turbulence and down drafts. You might want to review FAA and other publications on mountain flying flight planning and operations.
Another great video... no fear of the RED KNOB
https://www.youtube.com/watch?v=_VfiPuheeGw
Have a fun safe flight.