How tall, on average, are elves?
>How much variation in height is there?

What do elves look like?
>What skin colors can they have?
>>Is it just the same as human colors, or can they be purple or green?
>What hair colors can elves have naturally?
>>What eye colors can they have?
>What would be the best way to describe their facial features?
>Can humans mimic the appearance of elves using makeup and costume prosthetics easily, or are the two species too different?

Do elves tend to be more chaotic or more lawfully aligned?

Do elves have a strict social hierarchy?
>What is the hierarchy?

Are elves naturally skilled at anything?
>Toy making?

Are elves naturally athletic?
>Are elves naturally dexterous?

What are elves’ relations with other species/races?
Are elves able to breed with other species/races?
>How do they treat the resulting offspring?

Can elves touch and use iron, and alloys with iron, or does it hurt them?

Are elves capable of lying?

How much sleep do elves need?

What do elves eat?
>Can humans eat this as well or would it be bad for them?

How quickly can elves heal?

And of course, make sure to flesh out their culture, government, and homelands.