i had trouble at first too
and i always got freaked out and thought that something was wrong with me and i'd stop
but now there are no problems it was easier than i thought =)
Pull one string and leave that light on for a long period of time, pull another string and leave it on for a shorter period of time and dont pull the other string at all. The bulb that is the hottest is operated by the first string, the warm bulb is operated by the second string and the cold...