Things I found out the Hard Way

There's a lot to learn about this game. Most of my learning comes with a diploma from the School of Hard Knocks. Here's a short list of some of the things I had to learn the hard way in this game.

• Trade skills are king! This is doubly true for the secondary skills like cooking, first aid and fishing. Although it gives you something to do once you reach the level cap, there are better ways to spend your time than killing level 6 boars for boar meat so you can learn to cook. Likewise for killing level 8 humanoids so you don't have to buy the linen cloth to level your abysmal first aid.
• Bind on Equip greens can sell for a lot of money. Or at least more than the vendor will give you.
• As soon as you finish an instance, repair. You never know when you'll go to your next instance.
• PVP servers are not for me.
• Battlegrounds are fun (see PVP servers)
• If you don't feed your hunter pet, it will get so angry it will eat you. (Okay, not really, it'll just slink off and find its own food. And don't even think about whistling for it again)
• Add-ons good. Trying to play a level 40+ character with default UI bad.
• There is no such thing as too much RAM.
• Don't live with bad choices in your skill tree. Respec.
• Sometimes doing the math and making all the "right" choices leads to less fun. Don't be afraid to be sub-optimal if you're having a blast. This is an entertainment medium.
• Sometimes people die. No matter how good a healer you are.
• No one EVER runs towards the tank when they have aggro. No matter how many times they've been told.
• Sometimes when the encounter just isn't working, it's better to call it.
• Leveling speed isn't a race. We all encounter the game at our own rate.
• Watch for upcoming patch notes and understand what they mean. Otherwise, you'll get a 250G deal on the plans for an Arcanite Reaper (retail a few weeks before the patch). In fact, you'll probably buy two and plan to sell one after "the price stabilizes." Instead, you'll be lucky to make 80G after the patch.
• Don't try to control the market -- no matter what Auctioneer says.
• Auctioneer can help you spot deals
• Auctioneer can help you lose lots of gold.
• Some people are just not nice.
• Sometimes people give you crappy advice (on spec, on talents, on spell rotations, on gear, on well...you get the idea)
• Always have an enchant on your gear if you are leveling an enchanter (or know one who is leveling)
• Always have potions of the healing and/or mana variety.
  
• Drink elixirs if you're leveling an alchemist (or know someone who is)
• Eat buff food.
  
• Sometimes things don't work the way you think they do.
• As long as the gear you have is allowing you to progress, don't take too much time getting better gear. All gear gets replaced eventually.
• Take more bullets than you need.
  
• Laugh more often. Sometimes it just isn't that serious.