Let's get cracking. This walkthrough will direct you from start-to-finish of the entire game, but keep in mind that I won't discuss any sequence breaking tactics during the course of the walkthrough. If you're really itching for sequence breaking tricks you'll have to look elsewhere (or discover them yourself).
This run will also direct you to find every item the game has to offer and I'll describe everything in the context of Normal mode with references to Hard mode whenever there's a neat trick to be used.
When refering to item locations, each will be labeled with a short coding system containing the terminology below:
Eg. Missile Tank NO.05 refers to Missile No. 5 in Norfair as listed in the Missile Tank locations.
Spoilers are aplenty here as ants are to a sugary toffee on a summer's day so it's a good idea not to go reading on if you haven't played the game yet. Only check out areas you're really stuck in, and steer clear of the chapters beyond the defeat of Mother Brain unless you want the surprise spoiled. It's something you really should see on your own.
Please be warned - there are spoilers throughout this walkthrough, so only read it as a last resort.