To get past 225 you need to complete a quest, you need to be lvl 40 and have 225 skill.
For cooking you will be sent to Gadgetzan.
You will be told to collect several food items and then you get artisan training.
Might cost a bit of money since you'll need to buy some cheese, rest isn't too hard.
Fishing is in Duskwallow Marsh.
You'll have to catch 4 fish from all over the world, but it's rather easy
and for First Aid it's depending on faction but it's Hammerfall in Arathi for Horde.
You'll have to bandage a bunch of soldiers with the Triage bandages, tricky but not hard.
Also the Surgeon will teach you bandages when your best bandage turns green all the way up to Heavy Runecloth at 290.