if you're upstairs,and now you're getting downstairs , you can say下去。 when i 'm upstairs,and you're looking for me,you can call me 下来 if you need me to do something for you,you can ask me to过来 if you're awaken,you can 起来 or another situation,if you fall down,you need to 起来 if u still don't get it ,just comment here and i'm quite glad to help u :D

下去—go downward 下来—come downward 过来—come toward here 起来—rise upward

下去/下来/过来/起来 show the direction of action

Ok, I answered below to help you. After realizing the complexity of that. There is no simple response, so I found what I consider to be the best resources to start familiarizing yourself with those combinations and posted it. Good luck :-)

tl;dr -- best link http://comet.cls.yale.edu/mandarin/content/directional/grammar/direction-1b.htm NOTE: Depending on the VERB, the meaning can completely change, the rule can be broken, or it can seem pretty abstract. Exposure, reading more, hearing more is really the only way to learn it -- or acquire it. In a nutshell, the basic idea is that when you add those combinations to verbs, 來 will usually indicate you're already in a location/position speaking to a person and want them to perform the VERB in that same location. 去 will usually indicate you're in the same position as the person you're speaking to and want them to go perform a VERB in some location you're both not in. I stress** these combinations vary in meaning depending on the verb. Knowing the difference of 去 and 來 in how I explained it above should help you kickstart your understanding of when you to use 過來, 過去, 下來, 下去 etc. Links -- because there is no concrete universal rule. Reading about those combinations: http://www.chinese-forums.com/index.php?/topic/8700-complex-directional-complements/ http://comet.cls.yale.edu/mandarin/content/directional/grammar/direction-1b.htm http://forum.wordreference.com/showthread.php?t=503415 Practice Link: http://books.google.com/books?id=mNFNrTTD1n8C&lpg=PA91&ots=AU-VZZFI-w&dq=%E4%B8%8B%E4%BE%86%20%E4%B8%8B%E5%8E%BB%20%E9%81%8E%E4%BE%86%20%E9%81%8E%E5%8E%BB%20%E8%B5%B7%E4%BE%86%20%E8%AA%9E%E6%B3%95&pg=PA91#v=onepage&q=%E4%B8%8B%E4%BE%86%20%E4%B8%8B%E5%8E%BB%20%E9%81%8E%E4%BE%86%20%E9%81%8E%E5%8E%BB%20%E8%B5%B7%E4%BE%86%20%E8%AA%9E%E6%B3%95&f=true Godspeed my friend!