Quickly hide behind the low wall nearby, then head up the path and hide again. When the guard moves away, run over the path leading up. From here, make your way inside the building, wait for the guard to pass by and head upstairs. Near the top, wait for the guards to turn their backs on you, then move into the building on the far right.
Sneak route in the Mountain Temple area.
This triggers a scene with a Quick Time Event (QTE):
Xbox 360: Y, Y, move reticle and shoot with RT, wiggle left stick (left-right), tap X, press RT.
PS3: Triangle, Triangle, move reticle and shoot with R2, wiggle left stick (left-right), tap Square, press R2.
You get the [HANDGUN] after this scene. Move over the walkway to the east and climb the stairs to the top. You'll encounter two guards here that you'll have to take out. Lara automatically hides behind waist-height objects such as low walls, crates and boxes, so you only have to come out of cover by aiming and shooting enemies. Zooming in is done by pressing the right analog stick. There is some [HANDGUN AMMO] near one of the crates. Loot the bodies of the guards to retrieve some more ammunition, and make this a habit.
Head inside the building, head back out (that was quick, huh?) and follow the walkway. Don't miss the blue [HANDGUN AMMO] box along the way, as well as [ARROWS x2] and an [XP BOX]. Hide behind the cart and shoot the guard up ahead in the head with an arrow. This is a stealthy shot which grants bonus XP. This guide points out all instances when it can be beneficial to take a stealth approach.
Scramble up the wall, collect the [HANDGUN AMMO], then leap across the beams and climb up. Hide behind the crates and wait for the two guards to fully finish their conversation. One of the moves closer and turns around. Take him out with a headshot, then kill the second one as well. As the game explained to you just now, charged shots are performed by holding the right trigger while aiming. You can't indefinitely postpone the shot after charging, though. Once you start building pressure, a shot is inevitable.
Once you proceed, a third guard starts climbing down the wall. Quickly shoot him to make him fall. You can collect some [ARROWS] and [HANDGUN AMMO] before proceeding, and there's an [XP BOX] in the corner. Don't forget to loot the bodies either, then climb the rope ladder to reach the next open area.
MOUNTAIN TEMPLE - VILLAGE
Again, there are various items and collectibles to be found in this area. The nearby camp ('Mountain Temple') opens up Fast Travel, allowing to travel back to any and all previous base camps you've discovered. For now, you can only travel back to both zones of the coastal forest. Using the camp also unlocks [DOCUMENT - #2 LARA'S JOURNALS (NIGHTMARES)].
• You can find some [ARROWS] against the corner of the nearby building, and there's some [SALVAGE] between the building and the fence.
• Scramble up the wall and head inside the building (upper floor) to find some more [ARROWS] and a [GPS CACHE].
• There's an [XP BOX] and some [ARROWS] next to the barrels behind this building, not too far from the camp up ahead.
• Head back downstairs and jump into the river. Move through the crack behind the waterfall to find the [TREASURE MAP] of this area, as well as a [SALVAGE BAG], the contents of which you cannot claim just yet. Much later in the game you'll acquire the tools necessary to finally set fire to it, so make a mental note of it for now and don't go amnesic in the meantime.
• From the camp, jump into the river and look for a cave near the waterfall to find [DOCUMENT - #1 DIARIES OF A MADMAN (STRANDED)] and [SALVAGE] inside.
Move over the bridge and head upstairs; hide behind the low wall to overhear the conversation between two Solarii guards. It's usually better to wait for guards to finish their entire conversation, but this is one of those exceptions where it's wiser to shoot an arrow in the building behind them to distract them. Quickly shoot an arrow into the head of the left guard, then dispatch the other immediately afterward. If you don't do this, the guards will come down so you'll have to take care of them there. One of them only moves halfway down the stairs, so it's not too hard to stealth kill them either way. In any case, you can find [ARROWS] nearby when overhearing their conversation.
Making your way through the large house in the Mountain Temple area.
After this, move to the upper left side of the building (past the small cart with vases and a barrel) to move over a tree bridge. From here, scramble up the wall to find [ARROWS] and a [LARGE SALVAGE BOX] inside the building. Head back where you killed the two guards just now, and wait with going up the stairs. Instead, search the grassy area adjacent to those stairs (nearby a tree) to find a [PLANT]. Climb the wall here to find an [XP BOX], [HANDGUN AMMO] and some [ARROWS x2] underneath the roof. Move behind it (to the right) to find a [GPS CACHE] on the platform, nearby a single crate.
Go upstairs and scramble up the wall to enter the building. Collect the [ARROWS] and [XP BOX], then shoot the [PYROMANIAC LANTERN #1] to continue. Sneak behind the first guard and stealth kill him by pressing Y or Triangle when you're close enough to break his neck (by tapping X or Square). Do the same with the second guard nearby, then hide behind the boxes. There's a guard with a flashlight up the higher walkway and you don't want to be seen by him (yet). [ARROWS] can be found where you killed the first guard. From that spot it's also possible to hit a lantern in the distance, which is hanging near a white piece of cloth. These are all part of a challenge in this area; [PYROMANIAC LANTERN #2] is one of many, just like the first, and it can be hectic to get if you get into a firefight already. Shooting it instantly triggers a firefight (literally), so you may want to postpone it for now. On the other hand, collecting it now ensures you that you get this (missable) lantern.
Scramble up the wall on the left and shoot the guard standing still on the walkway (closest to you) whenever the other one moves away. As soon as he returns, quickly dispatch him as well (which may be tricky, but it can be done), preferably with a headshot. Lastly, dispatch the guard in the corner of the area. After this, several other guards appear including a true pyromanic who starts burning the place. Don't stay too long in one place and quickly defeat the remaining guards. After leaping over the gap (which leads to a zipline), turn around and look down to spot the lantern and shoot it.
Now that you're back outside, many more items can be collected in this area.
All collectibles in the Mountain Temple area.
• [DOCUMENT - #1 CONFESSIONS OF A SOLARI (SALVATION)] can be found to your immediate right as you drop down the zipline. It's on the crate next to the arch leading to the next area (to the southeast).
• An [XP BOX] can be found by dropping down to the left of here, on the river side.
• Wade through the water and move back up the wall in the back to find a [PLANT] closeby.
• On the southwest side you can either head downstairs or scramble up a wall. Head downstairs first and search inside the building to find the following [RELIC - #1 EDO PERIOD FANS (GREEN FOLDED FAN)].
• You can find some [ARROWS] on the roof at the back of this building. Jump on the rocky platform near the rock wall and face the building to spot another [PYROMANIAC LANTERN #3] hanging from (the lower back of) the roof.
• Light your torch and scramble up the wall at the top of the nearby stairs to find and burn a [SALVAGE BAG].
• You can spot the [PYROMANIAC LANTERN #4] hanging from the corner of this building's roof.
• [RELIC - #2 EDO PERIOD FANS (GUNBAI WAR FAN)] can be found by going around the building and entering the second floor.
• Drop down the ledge near the big wooden barrel and hug the wall, walking to the end to find a [PLANT].
• Leap over to the platform (with roof) to the far south to find an [XP BOX] and the last [PYROMANIAC LANTERN #5].
Move up the stairs to climb the mountain.