Dark Souls are used for 99% of all special mod items, weapons and armors you can craft, and usually in combination with other found materials. Good luck holding on to those souls. ;) 99% of regular Terraria content will be looted from chests.
Don't be afraid to use potions during normal combat.
Play with Auto-Pause turned ON (this will make reading signs and crafting stress free) and don't forget to use Quick Heal
Recommended Hot Keys: Pause/Inventory (R), Quick Heal (F), Quick Buff (B), Quick Mana (C), Grapple (E)
You may be able to fight a boss before you are able to beat it. If in doubt, continue exploring, leveling up your gear, and come back when you're stronger.
If you get stuck in sand in one particular area, use your mirror. You can also trying pushing your way through sand.
All boss summoning items are non-consumable so that you don't have to worry about running out of summoning chances. Just be sure to take the summoning item out of your hotbar during the fight to avoid accidently summoning 2 of them. :)
If you're playing on EASY Difficulty and you have a lot of souls on the line and want to tone down the intensity, you can put your souls in any of the safes found at many save points. Alternatively, SUPER EASY mode removes the "Souls drop on death" mechanic entirely.
You won't be able to craft everything on your first play-through, so you will need to make choices about what you want to invest your souls in.
Make sure you don't kill a boss while its head is passing through tiles, or you will likely not be able to recover them.
Max stacks for most ammo and potions has been increased to help with item management. However this applies to your inventory only. Keep stacks in safes at their normal level (250/30 etc).
If you're not sure where to go next, go in any direction you haven't been yet. There are rewards to find in every direction.
Keep an eye out for visual clues and secrets (there are many!)
You can farm enemies. You will not be able to farm bosses for souls. But you can farm bosses for the materials they drop if you want.
You can use your hammer freely.
The Greater Magic Mirror provides some major benefits for fast travel and convenience. Remember to use it often! It can also be used to return to a tricky spot quickly, if you can remember to set your spawn point. :)
You will die. Probably a lot. But don't stress it. It is part of the risk/reward satisfaction of the game. If I succeeded, when you beat this game (and every dungeon in between) you will feel a real sense of accomplishment and triumph.
You may want to keep your Cosmic Watch handy during a blood moon on Hard Mode ;)
If your map file gets corrupted (a very, very rare thing) go to Documents\My Games\Terraria\Worlds\tConfig and find your map file with the .bak extension. Remove the .bak to restore your map
Check the main Terraria Online thread every few days for the latest updates to the mod and map. There may be needed updates to your mod. If you have any questions or feedback, feel free to post it there. There's a pretty helpful community willing to answer questions, including me. :)