The sequence of columns in an clustered index

  Simplily say, If you have a CI(clustered index) which is composed by 4 columns, Which one of the 4 would you put into the first one in the CI? and Which would be put into the last? Or you shouldn't consider this question at all, just put them casually togather to form a CI?   Simplily say, If you have a CI(clustered inde