Say that the vector u is represented by
u = (ui , uj , uk )T
and that the vector v is represented by
v = (vi , vj , vk )T.
Then u × v = ( uj vk - uk vj , uk vi - ui vk , ui vj - uj vi )T.
There is a pattern in how this is formed. Look at it a bit. But don't even think of memorizing it.