Is there a specification somewhere listing the correct way to pass GET variables to a URL?
Normally I do it like this (first variable indicated by ?, second and subsequent indicated by &:
http://www.mysite.com/mypage.html?var1=value1&var2=value2&var3=value3
Are those ? and & specifically needed, and in those order? Could I eliminate the '?' and pass all variables only with the '&' ?
No, how you are doing it is correct.
http://www.w3.org/MarkUp/html-spec/html-spec_8.html#SEC8.2.2