Diablo 3 is a fairly simple game at its core, but there are still a lot of tips, tricks, and tweaks to discover that'll make your journey through the Burning Hells slightly easier. Here are some of our favourites.
If you're playing as a ranged character, sometimes you'll accidentally click on the ground instead of the enemy you're trying to attack, and end up charging towards them. To avoid this, and keep your character in place, hold the shift key while attacking.
Dungeons will always consist of the same number of floors, but every time you play them, the layout and locations of treasure, shrines, and healing wells changes. Enemy placement is also randomised, as is their HP, but they'll always be of the same level.
Wizards' signature spells don't use any arcane power, so you can keep casting them without pausing. The wizard has the fastest mana recharge rate of all the classes.
Hold the alt key while hovering over an item to compare two dual-wielded weapons, or two magical rings. If you have your follower window open, hovering over an item will compare it to the one they currently have equipped.
Grey items are worthless. White items are usable, but have no magical enchantment. Blue items have at least one magical property. Yellow items are rare, and have a higher base stat, and a greater number of enchantments, than blue ones. Orange items are legendary, and are never randomly generated; they always have a unique name, and specific properties. Green items are also legendary, but are part of a matching set. Collecting a whole set of green gear grants you a special bonus.
If you choose to dual-wield, you'll get a 15% bonus to your attack speed.
Your followers never die. If defeated, they'll drop to one knee. After 10 seconds, they'll revive themselves. Any health globes you pick up will heal your companion.
In co-op, gold and loot are unique to you. Items dropped by monsters or chests are yours and yours alone, and only you can see them on the screen. If you take an item and drop it on the ground, it'll be visible to everyone.
If you aren't using voice chat, you can still communicate with other players. Use the numeric keypad to select from a variety of useful stock phrases. Thanks, sorry, etc.