this could be useful http://www.answers.com/Slovak%20Language no ale skus to vysvetlit takej cinanke...

The rule is simple: "sa" is accusative = Vidím sa v zrkadle (vidím koho/čo) "si" is dative = Dám si pivo (dám pivo komu/čomu)

Well, I am a native Slovak as well. I guess or the only rule I can think of right now is: We use "si" with the verbs like think - myslieť; wish - priať, želať; but also with verbs that imply that you do something for yourself or on your own such as „We are going to have a party“ – „Urobíme si párty“; And something more confusing with difference in meaning: „Look it up in a dictionary (for yourself)!“ – „Pozri si to v slovníku!“ versus „Look at the sky!“ – „Pozri sa na oblohu!“

hum...i know! juts slike i and y right? aye!its really not easy to learn!~ :(