Free the White Queen:
To solve the final part of the puzzle in the dream sequence where young Lara breaks into her own house you have to go back to the globe and move it away from the correct co-ordinates in order to make the ladder retract and free the White Queen.
Easy Stealth Kills:
If you pick up the skill Viper's Snare you will have the ability to boobytrap bodies by setting an explosive charge on a downed enemy so that whenever his comrade approaches it will blow up killing them and give you a stealth kill.
Find the Explorer Backpacks:
The Explorer Backpacks reveal the location of ALL Crypts, Treasure Chests, and Survival Caches on the map. This makes finding the backbacks a priority as it will save you time having to look for the collectibles whereabouts.
Raposa's Wit Skill:
Try to pick up the Raposa's Wit skill as early as you can as this allows you to unlock the next tier of weapon upgrades.
A headshot is the best way to kill smaller animals and humans but with some of the larger animals you will bring them down quicker if you shoot them in their heart. If you don't have the perk that shows you the animals beating heart you can always guess it's whereabouts.