For this you must have at least 45 cooking.... this is what you do...
Step 1--- Buy 5k raw trout
Step 2--- Members- Goto Karamja island and into the Tzhaar area and use the sulpher vent near the bank
Non-Members- Varrock Castle where you start cooks assistant
Step 3---Cook the 5k trout (will not burn because of such high cooking)
Step 4---Selling the 5k cooked trout back and then use the money to buy more
Step 5--- Repeat until about 75 cooking
Step 6---74-94 cook Lobsters (TIP: buy 5k cook 5k sell 5k repeat!)
Step 7---Cook raw shark from 94-99
Step 8--- Go buy your 99 cooking cape!
Hope this helped since i broke it down into 8 easy steps, just post what you think and tell me what didnt make sence if your stuck (its kinda straight forward so...) it would be appreciated it you +rep me for it but its up to you

Happy cooking!
User has double posted, the second post is below:
oops sorry the name was wrong :P i meant 99 cooking!