Being a Alchemist in WotLK
If you’ve done Alchemy up to 350+ one does not have to tell you how to be a Alchemist. Anyway all the new recipes you can learn from the new trainers in the starter areas and later in Dalaran. If your a Herbalist as well those are your 4 most valuable herbs that you need to constantly flower pick when seen or spotted for your self to do constant Alchemy Research as a Alchemist to discover new Potions/Elixirs/Flasks under the new discovery system. Can be valuable to sell if your a Herbalist and not a Alchemist as well.
So if your a smart Alchemist you should stock up on those herbs if anything and on every cooldown do Alchemy Research to discover something new with the side effect of some new potions created. The faster you do that on every cooldown the faster you will have all the new to play with Potions/Elixirs/Flasks. That also means the earlier you can use or sell some your new brews in the new economy and make some money. Helps to be good at making money as well in skills selling your stuff.
If your a Alchemist with good economic skills and a have mining or a pocket miner. You can do well burning up that Transmute on every cooldown (4 days) to make lots of Titanium. It will be heavily used in lots of things especially in making Titansteel and other valuables. Of course one does need to constantly pay attention to your economy Supply, Demand and Over Supply & Demand can help or hurt your wallet. Be smart.
Cobalt will be found everywhere just about. Saronite can be found in Scholazar Basin (lots) and the last 2 zones. Exploring caves are always nice (tip).