Instead of trying to remember what 3 you need to do it's more helpful to know exactly why you're doing each one.
1. Alt pos to battery pos -- the only positive run for the big 3 and is necessary to supply current to the rest of your system.
2. Vehicle chassis to battery neg -- your vehicle's chassis/frame needs to be grounded as that's what multiple electrical components both factory and aftermarket use.
3. Alt casing/Engine block to battery neg -- in order for your alternator to charge it needs a grounding point. The casing on the alt is used as a ground. Most people will attach a wire to the engine block because the alt is bolted onto the engine block. For minimum resistance, find a bolt that is NOT the alternator positive terminal, and attach it there.