Stamina: call each Extreme Healing Radio frequency once when your stamina runs low: 140.16 and 141.42, 142.42 and 145.18, 146.45 and 148.66, 148.78 and 149.39. Each refills a large part of the gauge on its first call only. Silent steps: equip a grenade and hold the weapon button (Square on PlayStation) without throwing: while Snake holds it ready, guards don't hear his footsteps. Peeking: lean round corners and over ledges with the lean buttons (L2 and R2 on PlayStation) to line up headshots unseen. Ammo: ammo drops follow the guns you carry, so leave the lethal guns you won't use on the ground and the Mk22 gets more. Uniforms: AUSCAM takes a third off the damage you take, DPM doubles life recovery, Flecktarn gives the goggles endless battery and Desert Tiger endless suppressor use. The biosensors don't work on Extreme, and guards see much further, even at a 50% camo index: slow is fine, the five hours are generous.