How do I use the clutch claw?
The clutch claw has a very limited range. Use it when you're close to the monster. If the monster moves or attacks, you will be injured or even killed. Use it when the monster is winding down from an attack or when it isn't moving. You also use stamina while clawed on and will fall off if it depletes. All weapons can use the clutch claw while the weapon is unsheathed, so you can work it into your existing combos and claw on when you see an opening. You'll get better at this as time passes.
There are several parts of a monster you can claw on to. It can be difficult to actually aim when it's moving around so you may grab the wrong part. You can move along the monster with the control stick the same way you do when mounted. Pressing triangle (PS4 controls) will do a slashing attack and dismount. With "heavy" weapons, you will immediately soften the monster's part; with "light" weapons, you need to do this slash attack twice to soften. A softened part takes additional damage similar to a weak spot. It eventually becomes unsoftened after a short time. You can tell if it's taking softened damage because there will be a little square of ticks around the damage number. This attack is very useful for creating temporary weak spots on monsters that have poor hitzone values along large parts of their bodies.
The real fun of the clutch claw is slamming the monster into a wall. Claw onto its head when it is not enraged and press circle (PS4 controls) to make it swing around in a 45 degree angle. You can do this several times to get it to face the way you want. When it's facing the way you want (facing a wall or other obstruction), press R2 to unload your slinger ammo into its head. It will fly forward a good distance. If it hits a wall while it does this, it will take heavy damage and fall over, being immobilized for several seconds. This attack is invaluable for heavy damage and stunning the monster and should be spammed whenever it is unenraged. Often, a monster will become enraged immediately after you do this attack, whether it hit a wall or not. Make it count.
What's this Steamworks thing? Is it just completely RNG?
Outside the gathering hall in Seliana is a contraption called the Steamworks. You put in "fuel" that you earn from quests (this fuel serves no purpose beyond the Steamworks, so feel free to use it all) and then you "press" three buttons in sequence to earn items, meal vouchers, etc. This process is completely random. There is no secret to guessing which button you need to press next (except for the occasion where the cats jump up and show you which to press). You can just hold down the button and let it run. When the bar is fully filled red, you'll hit "overdrive" and receive a bonus reward. Each week, the first time you get an overdrive, you receive a Celestial Wyverian Print that can be exchanged for a rare monster item of your choice (mantles, the MR equivalent of gems).
This Guiding Lands thing is really confusing. Where do I begin and what is my goal?
The Guiding Lands is a new map you unlock at the end of the game. It is divided into four regions that are based on the Ancient Forest, Wildspire Waste, Coral Highlands, and Rotten Vale (two additional areas based on the Elder's Recess and Hoarfrost Reach were later added in DLC). These regions each have a "level" that grows as you kill or capture monsters, break their parts, collect their tracks, and do other assorted activities in that region. When a region levels up, stronger monsters appear. At levels 1-3, you fight monsters of increasing strength; at levels 4-5, tempered monsters from the first three levels will begin appearing; at level 5, elder dragons will appear; at level 6, a unique "apex" monster that rules each region; and at level 7, tempered elder dragons. The Guiding Lands is considered an expedition, and therefore there is no set objective to complete. You can hunt monsters endlessly for hours if you so choose. You can die an unlimited number of times without failing or losing anything, but if you die you will receive fewer rewards after killing the monster. Note that you can exploit the Fortify skill to receive a free boost to your attack and defense the first two times you die.
Three monsters can appear in the Guiding Lands at any time, and they are completely random. After you kill or capture a monster you will receive a random "lure" for a specific monster. You can then talk to the Handler at camp to use a lure to make a specific monster you want appear. When you fight monsters in the Guiding Lands, you will notice they drop items the way a pinata drops candy. These items they drop everywhere are unique to the Guiding Lands. Every monster has a unique Guiding Lands material that it drops here while it is being fought, and the tempered versions also have a unique material. For example, a Rathalos fought in the Guiding Lands will drop "King's Scale," while a tempered Rathalos will drop "Tempered Red Scale." These Guiding Lands materials are used by certain weapons for their highest upgrades, as well as for the new augmenting system (see below). Once you've fought a monster in the Guiding Lands, you can also meld for its parts at the Elder Melder. Monsters also drop assorted bones and "Spiritvein Gems" that are used for augmenting weapons. As a quick tip...for some reason, equipping a single point of the Geologist skill will allow you to pick up shiny objects twice instead of once. This was thought to be a glitch but for some reason has never been patched on consoles and will presumably still work on PC.
When you level up a region, eventually other regions may start to decrease in level. It is not possible to have every region at level 7 at the same time, for example.
What is the new augmenting system?
Like the base game, fully-upgraded weapons can be augmented, but the system is MUCH friendlier than the old way of having to grind for super-rare things from tempered monsters. Every weapon starts out with three "augment slots." You can fill these three slots with an attack boost, defense boost, affinity boost, elemental/status damage boost, or an extra decoration slot, and each of these things takes up between one and three augment slots. When you've filled all three slots, you can choose the "Extra Slots" option to purchase more upgrade slots. Note that like the base game, Rarity 10 weapons have the most available augment slots, Rarity 11 weapons have fewer, and Rarity 12 weapons have the fewest. The materials used for augmenting are entirely obtained from monsters in the Guiding Lands.
However...there's another twist to all this. Weapons that do not have unique appearances can be augmented even further with a system called custom augments. Custom augments add a little boost to attack, defense, affinity, or elemental/status damage and also change the weapon's appearance. You can stack up to five of these custom augments (later bumped to seven following DLC updates).