Farming deviate fish in any of the Barrens oasis and then selling it on the auction house to the Alliance, or on your own auction house if you're already Alliance is a great way to make some extra silver extremely early on. I haven't found it to be any significant amount, but it can definitely help your initial bag/spells/profession/etc costs as a new toon.
Here are a few extra tips I found helped me acquire more gold.
Good general guidelines and overview of what players should know. As mentioned, there seem to be a lot of tailors right now so competition in the bag market is fierce, especially for Small silk Packs and smaller. On my server many tailors are offering to make bags for players so long as you provide the cloth (and leather, for Silk bags). It helps them level Tailoring and since you will be getting cloth anyways it’s a good deal for everyone. But don’t fall into the trap of getting bigger bags only to carry around more stuff. Keep them as empty as possible when you go out questing (and moreso if you’re heading to a Dungeon). Only keep necessary potions, food and bandages on you if you can help it. The more space you have, the more room you will have to collect loot to vendor or sell. Nothing it worse than having to delete items you could sell just because you are far from a vendor.
A bank alt is incredibly useful. Mail everything to them that might sell and stick it on the AH. Use Auctionator (or maybe another AH addon) to easily post stuff for a price that sells.Be really wary of AH deposits. Lots of items don't sell for enough and/or don't sell consistently enough to not risk losing that deposit. That's why you're often better off just vendoring some items.Important detail: there is no deposit for enchanting materials so if you are an enchanter or your bank alt is an enchanter you can safely list and relist those until they sell, with no downside.Make sure you train your skills with a trainer you're honored or better reputation with. Druids in particular have to avoid the trap of using the neutral trainer in Moonglade where you'll miss the 10% discount which really adds up in the levels before getting a mount.
Wow this guide needs to go. The classic economy is already screwed up and is absolutely nothing like vanilla was. This isnt needed, people are greedy enough as is.
Classic has thrown the WoW economy to the dogs. There are so many players all about the same level gathering and doing professions that pretty much anything gathered, made, or dropped ends up getting vendored. Even hard to get things like the Big Iron Fishing pole (which is REAL pain to get) was selling for under two gold. Most armor and weapon drops do not sell and even blue items are not worth as much as they should be. The worst of it is that the crowds will slowly go away as they struggle with leveling, boredom in traveling, and the high difficulty. This will create a smaller marketplace for the AH when the real gold and rare drops starts rolling in at the highest levels and people can afford to buy stuff.
A new economy is always tough. Remember, this game hasn't even been out a month! Things will level out over time.
I would recommend keeping high level BoEs and expensive drops from 60 level dungeons, remember Classic has no catch up mechanism and it's a matter of time before there are barely dungeon runs so people will have to go to the AH.