It is highly recommended you have a thorough understanding of how the strategy elements and mechanics of the game work before attempting the game on Grounded Mode.
What's different in Grounded mode?
+ Listen Mode is disabled. That's right, the Listen mode that you got to love during your normal playthrough is gone. You will completely rely on hearing the enemy or need to memorize their movement patterns. It's the same as on 'Survivor' difficulty.
+ The HUD is disabled. That's one of the reasons why I recommend beating the game on a lower difficulty first. You don't need the HUD if you know what you're doing. Also unchanged from survivor difficulty.
+ All enemies do triple damage. You will want to stealth it whenever possible. Open confrontations usually mean that you will get destroyed quickly.
+ Multiple mid-combat and mid-stealth checkpoints have been removed. Probably one of the biggest (and most frustrating) changes to survivor difficulty. Remember the fight during 'Winter' with Ellie? Imagine having to do a whole sequence (usually leaving the room or anything involving a cut scene starts a new encounter) in one go. Yep, it's gonna hurt.
General tips for the walkthrough:
+ Learn the patterns of where enemies are. In the wharf when you're after Robert, there's around five or six and all except the last guy can all be killed quietly. The last guy, just run around the corner and melee him. Your surprise attack will win. When you make it to Downtown and you have to clear out the infected before Ellie and Tess can follow, there's three roaming runners, one stationary runner and one stationary clicker. I'm not gonna lie, sneaking up on roaming runners in the hardest thing, but it's doable, especially here.
+ When you get to the bookstore full of hunters, forget about killing them all to loot the area. You won't get much loot anyways. Use stealth to take out the few that are in your path and then use the bow and arrow to kill the guy guarding your exit.
+ Don't bother modding your melee. You'll find a lot of melee items along the way and shivs or bombs are more important. I only had one modded melee the entire game and that's the one you find in Bill's Town.
+ Because you don't have a HUD to show how much health you have, it's difficult to know how hurt you are, but if Joel is holding his side, it's a safe bet that one hit will kill him. Choose between a molotov or health kit as needed and don't immediately craft items just because you have the materials to do so. On more than one occasion, I was able to craft every item, but chose not to because I wasn't sure what I'd need later.
+ Conserve ammo and crafted goods whenever possible! It will make the last encounter SO MUCH easier. I arrived at the hospital with two molotovs and three smoke bombs. Due to Grounded Difficulty you are already looking at a rather long route to the checkpoint, being able to toss a smoke bomb to get past some of the guards quickly prooved to be a real advantage.
Again: Don't use crafted items if you feel like you can beat an encounter without using them!
Let me know if there are encounter's you are having issues with! I can provide some more information on them or add them to this solution.
Good luck. :)