Heirlooms can certainly be used with our guides! You may find yourself getting ahead of the guide. If you start doing gray quests, just skip ahead to a later zone. The guide is just that - a *GUIDE* not a rule, as many people seem to think. Feel free to skip parts! Watch out for quest chains, though, especially in the last part of the 50-60 section. Hopefully we'll have some awesome features in our new addon that will make it easier to skip around!
The expansion brings a major change to the PvP ruleset on each realm. Every realm by default only allows players to attack NPCs in the open world; players who wish to engage in world PvP now have a setting called "War Mode" that can only be toggled on or off in their faction's capital city (i.e. Stormwind for the Alliance and Orgrimmar for the Horde). While in War Mode, players have access to new talents and abilities, as well as a slightly accelerated rate of XP gain. Characters with War Mode activated are only able to see other players with War Mode, unless in their own capital cities.
The most important part of saving is to never buy equipment unless you're positive that it will increase your earning potential, or significantly speed your character's leveling progress. While it is true that gear is important (particularly for melee combat characters), it is also true that an overemphasis on having great gear before maximum level is dumb. Who cares if you're wearing a green sword at level 43? If you're advancing well, you aren't going to be level 43 for very long anyway. The only gear that currently "counts" is max level gear.
When assigning a selling price, do not aim for too low a price that would give you too little profit, but certainly do not assign too high a price. Too much greed is never a good thing, and the AH is filled with items that do not sell due to excessive inflation. A very common tactic in the AH is to sell for lower than what another player is offering, and many players make a lot of money that way. Similarly, losing sales thanks to being undercut is never fun. Aim for as low a price you can that will still make you a good profit. If you can keep producing the same item over and over, sell cheaply yet make a good amount of the item, you will reliably make a lot of money by volume. Moving inventory is the best kind of inventory.