Check Item's Vendor Price before posting it on the Auction House - Selling items on the Auction House below their Vendor value is a common mistake. Avoid it like fire, and always make sure that you are not losing Gold on your Auctions. If you plan to sell an item on the AH for a price just a tiny bit higher than its Vendor value, you might be better off just vendoring the said item (this will allow you to avoid the risk of losing an Auction fee if your Item doesn't sell).
I made some route changes to the Horde levels 43-44 sections. I have swapped 44 Dustwallow Marsh with 44 Desolace (the entire sections). This allowed me to do Deadmire (at lvl 43 instead of 38) and then go stop at TB to turn in Deadmire + The Black Shield at the same time, then fly quickly to do the Desolace stuff. Doing 44 Desolace is now mandatory because I think its faster with the new routes. This will also make the level 53 grind much shorter. I think these were great changes.
That's not to say that everyone has an unrealistic vision of what vanilla WoW was like. There were already plenty of people on the WoW Classic forums pointing out that perceived bugs are just recreations of the original game. And as noted before, a flaw to one player is a key component of the original positive experience to another. WoW Classic will surely please plenty of purists in spades. But this goes to show that it won't be for everyone who has fond memories of the game circa 2006.
Upgrade your bags as quickly as possible - This tip is closely connected to the previous one. Upgrading your bags quickly will ensure that you spend more time grinding and less time managing your inventory, which will increase your leveling speed and allow you to make some more money in the process. Bags are expensive, so it is a good idea to look for a Tailor who will make you a set of new bags for Materials and a small fee (you will surely loot some Cloths, so this will not cost you too much). There are also some Quests that reward you with Bags:
Plaguebats (marked BLUE on the map) - These Plague-affected beastly flying creatures roam southern parts of the Eastern Plaguelands. Slaying them will provide you with a lot of Vendor Trash Items (Evil Bat Eye, Bat Ear, Sleek Bat Pelt, and Large Bat Fang), Wicked Claws (used in Leatherworking and Blacksmithing Recipes), and maybe some 16 Slot Bags. Bats can also be Skinned for Rugged Leather, Thick Leather, Thick Hide, and Rugged Hide, so Skinning Profession is recommended for this Spot. Plague Bats have access to the Terrifying Screech Ability, so they can get annoying at times, especially for melee Classes, but are a great source of Gold nevertheless. Recommended Level - 53+.
Monstrous Plaguebats (market GREEN on the map) - These are larger cousins of the normal Plaguebats. They occupy northern parts of the Eastern Plaguelands and drop Vendor Trash Items (Evil Bat Eye, Bat Ear, Sleek Bat Pelt, and Large Bat Fang), Wicked Claws (used in Leatherworking and Blacksmithing Recipes), and maybe some 16 Slot Bags. These can also be skinned for Rugged Leather, Thick Leather, Thick Hide, and Rugged Hide, so Skinning Profession is recommended for Farming them. Monstrous Plague bats have access to the Sonic Burst ability, which is a 10-second Silence, so they are not a good choice for Spellcasting Classes. Recommended Level - 56+.
Some players have been surprised by these apparent flaws—even players who have been eagerly awaiting WoW Classic's release based on fond memories of vanilla WoW. In truth, it has been so long since WoW first released, players' memories may not always be accurate. Some details might be fresh, but others might be lost in time, and it's those lost details that could surprise players revisiting the original experience in WoW Classic.