Diablo3Blog has posted a great list of over 50 Diablo 3 tips and hints, here is a little taste. After check out Diablo 3 Tips for the full list.1 – CTRL + Mousing over and item on the ground (outside of inventory) shows stats so you aren’t forced it up. (kallell)
Doing this while having your inventory open should compare the item on the ground to what you currently are wearing as well. (broken1000)
2- There is a “force move” (labeled “Move” and is unbound by default) button that is unbound by default. This is helpful for running through packs of monsters and not accidentally clicking and attacking one. (need to manually bind) (kallell)
3- You can link items by bringing up the chat text box and shift+clicking an item, making it easier to show items to people to see if they need them or if you're in different areas. (twincannon)
4- If you think you have an upgrade for someone you're playing with, instead of asking him you can inspect him by right clicking his icon on the top-left. (twincannon)
5- Whites/grays sell for next to nothing and really aren't worth the inventory space outside of the first act, just toss that junk for less town trips (make sure to check the prices in nightmare mode and beyond though, who knows if this will change later on). (twincannon)
6- Buy +2-4 damage magic rings ASAP, they're pretty overpowered when they become equippable at level
6. Restart the game a few times if they don't show up, or if they give a poor secondary bonus. (twincannon). Buy @ Radek the Fence: http://i.imgur.com/C0VXGh.jpg (Sf4tt)
7- Never sell magic items to a vendor as the crafting mats will probably sell for more in most cases (will change in retail but in beta, magic stuff sold for 50-75 usually and the essence sold for 150). Also rumors that you can trade the essence upwards, i.e. 10 normal mode essence for 1 nightmare mode one. (twincannon)
8- Dont waste money on bigger stash early on, make mules to hold items, (twincannon)
9- If leveling up with a friend, designate one of you for leveling up the jeweler artisan (JC is MUCH cheaper) and one for blacksmith artisan, saving half the money required. (twincannon)
Although I don't remember the exact numbers, the Blacksmith will require about ~700,000 gold to level up to max, while the jeweler will only take about ~45,000. (tolvinar)
10- You can hold left click to run around and simply tap shift to "stutter walk" fire instead of clicking the mouse (holding shift and casting will make you cast the ability in place,), works well for ranged characters to give your clicking finger a bit of a break. (twincannon)