Wait, /sit to trigger crits is p-server thing? I distinctly remember people saying that if you sit, you will be crit when I played 1.12 Vanilla. On top of that - there’s that pally that one shot Kazzak in early Vanilla because he stacked a shitload of reckoning when it didn’t have a limit - it’s not inconceivable that he did it without /sit to trigger crits, but it would take him so, SO long to do that without /sit.
Swim Speed Potions (used especially at lvl 37 for Faldir's Cove in Arathi Highlands and lvl 57 in WPL). Try to get multiple stacks of these. I also recommend keeping a stack of these always in your bags. You will frequently pass rivers and lakes and can use these potions to pass them faster through out the guide. Please note that these potions do not stack with Druid's Aquatic Form and Glyph of Aquatic Form.
Blizzard’s stance on old-school servers wasn't always so eager but evolved due to fan demand and the arguments presented in their favor. Somewhat infamously, Brack himself said “you think you do, but you don’t” in regards to the desire to play older versions of WoW back in 2013, and the internet hardly let him live it down until he personally announced World of Warcraft Classic at 2017’s Blizzcon. So does the sentiment that you can’t go home again still hold water in regards to WoW Classic?
Earning gold in World of Warcraft: Classic is all about optimizing your spendings. Back in the day, your character’s skills were acquired from a trainer, using money. Don’t just buy everything he or she offers! Read the skill descriptions and be mindful about them. Quite a few characters can live through the levelling process without learning some of their utility or damage spells. These won’t go anywhere and you’ll be able to learn them later on.
Note: My goal here was to create a comprehensive list of everything you'd need in order to learn to play any class (from Level 1 to Naxxramas)—meaning I am only including class-specific resources here (so no profession guides, general leveling guides, etc). Teeb's Resource list is much broader in scope, and I highly recommend you take advantage of it (as it contains a plethora of non-class specific resources as well). If you're not aware, Teeb is also responsible for the Race & Class Comparison Tool, Dungeon Tier Sets Gallery, and a huge variety of other insanely useful resources.
HOWEVER, I did find out that there was an exploit to get around it (one of those rare exploits where you would WANT a bit of lag). Basically if you spammed “X” to sit/stand/sit/stand, then if a mob hit you while you were sitting and right as you were standing up, then it would register as a crit, but on the server side you would be standing, thus allowing the ability to proc.