I have read about the staff on another site. The author referred to the staves as "He or she". Does this mean staves are, in a way, self-aware?
not self aware like it's a living object, no. the tool has your energy charging it, so you will feel a connection to it. different items also represents different sexualities, it doesn't mean the tool is a boy or girl, its just common to categorize it as masculine or feminine. i don't use a staff but i think it's masculine. [further examples, the chalice would be feminine, the Athame masculine, the bell feminine]
Must wands be straight or wonky lengths of wood or metal? And nothing like, say, a flute?
wood is traditional but i've seen it made from metal. it needs to be made of a single branch, not a bungle of twigs bound together. use what you feel drawn to.
Let us pretend that I have declared a shiny kitchen knife my Athame. Then, another day, I wanted to use a shiny bayonet for spellworks. What do I do?
slightly confused, you mean one day you dedicate one item, the next day you grab a random object to use instead? you should stick with the tool you dedicated. like with the wand, it should be an item you are drawn to, not just a random butter knife from the kitchen. if many years down the line you feel drawn to another Athame, you can use that one too, but your Athame is a sacred tool and shouldn't be cast aside for the shiny new model. [but if you accidentally drew blood with it, many Wiccans believe its been tainted and should be destroyed or re-cleansed and rededicated]
Speaking of which, is an athame and a sword the same thing?
no. the Athame is a small double bladed, black handled knife that can be held in one hand. it is used to direct and cut energy only. the sword is longer, and is used in rituals, and cuts physical objects like cords. to become more confusing the Boline is a white handled, curved blade, roughly the same size as the Athame, and it is used to cut herbs and items for spells.
just out of curiosity, what book were you reading exactly?