Bit late to remember something now, Lara...
You know what it's like. You find yourself deep in the frozen bowels of Siberia, and wish someone had told you to pack a thermos of Earl Grey before you left the house. That's a bit like Rise of the Tomb Raider. But instead of tea, it's weapon upgrades, controls and knowledge of enemy behaviour. Yes, that did escalate quickly.
Well, I can help with that. Having finished the game, there are loads of things I wish I'd been able to tell myself to save some time and hardship. So allow me to impart my wisdom. If you want, you can pretend it's like you've found one of the story documents. Yep, by all means read each entry in as dramatic a voice as you can muster, for maximum authenticity.
Raid the tombs (I'm not even joking)
The challenge tombs are optional, but that doesn't mean you should save them for something to do after you've completed the main story. They are certainly harder to find than in the last game, but when you get the notification that one is nearby, get in there. Whatever peril the rest of the world is in, it will wait until you've finished.
Each tomb gives you a useful skill that'll make playing the rest of the game either easier or quicker, so it makes sense to have Lara's abilities progressed as far as possible as soon as possible, otherwise you'll simply have everything at your disposal after the adventure's long finished.
You can switch shoulders with the left stick
A simple click of the left stick will shift the camera to your other shoulder. It's amazing how much more visibility this can give you when you're behind cover.
It's also worth noting that the position of Lara's muzzle or arrow tip on the screen as she's preparing to fire doesn't matter at all. Whatever enemy or scenery is aligned with the crosshairs will register the hit. Yes, even if that wouldn't be physically possible.
Hunt whenever you can
It can begin to feel like hunting isn't really necessary, especially if you don't care much for different outfits, but seriously, it helps to have as many hides in your inventory as possible, because they help you upgrade your equipment. So basically, even though it's sad (or fun depending on your mentality), keep shooting the bunnies.
The Arrow Retrieval skill will let you reclaim arrows from successful kills but it won't get back the ones that miss. So be accurate, or you'll quickly run out of ammo.
Don't forget about the Supply Shack
Early on, you find this shack in the Soviet Installation hub area, in which several pieces of equipment are on sale. To buy them, you'll need to collect Byzantine coins, so you'll only be able to afford one item (if anything) when you first happen upon it.
However, it's very easy to forget about the shack as you progress through the game. Sure, sometimes it reminds you that new equipment is available to buy, but you're hardly going to stop what you're doing and head there, right? Well... actually, you probably should. You can fast travel at any time from a campfire, so go back regularly and improve your arsenal. How should you do that? Well let me tell you...
Buy the red dot sight for your rifle
Conversely, I don't believe the suppressor for the pistol is a great purchase. Sure, it's quieter, but guards will notice their friends dropping dead beside them, so it's better to use stealth takedowns, luring guards away from the group and killing them in the bushes.
Unlock the following skills asap
The simplified skill tree system has some very useful perks early on. You should get the Thick-Skinned skill to take less damage from enemies, Fast Healer to bandage yourself more effectively, Breath Control to increase your fully-drawn, steady aim time on bows, and Lightfoot for landing safely from relatively high places. Finally, the Avid Learner skill is useful for an early boost to your XP gathering.
Other skills aren't particularly useful early on, such as the Efficient Killer, which automatically loots enemies when you stealth kill them. It really doesn't take long to press X over a dead body and pick it up manually - that skill point could be much better used elsewhere.
Unlock Deadly Force asap too
This perk is found in the second tier of the Brawler skillset. When you start the game, you can kill people with your bow from behind, but you need to keep tapping X to finish them. With Deadly Force unlocked, however, you can kill quickly and efficiently. And also smash people over the head with empty bottles. Lara really has clearly been watching Nathan Drake...
Although I don't remember Nathan Drake hitting someone with a bottle and then glassing them in the throat. Lovely girl, that Lara.
Distractions only work on the closest guard to them
If two guards are talking to each other and you have an empty jar or bottle to throw to distract them, only the closest will check it out. So if you throw it past the one farthest from you, you can stealth kill his buddy before he's even reached the broken bottle, by which point you'll have killed him too. Nobody tells you this in the game, but it helps so much as it can be exploited.
Need something a bit stronger?
No, I'm not still on the tea analogy. I mean we have actual guide content that will tell you where things are in Rise of the Tomb Raider. Don't be ashamed, it isn't fun being stuck looking for one thing.