There are Tagalog expressions that you will only learn as you live with the native speakers of the Filipino language. You may not even find them in textbooks which only deals with the formal way of using the language. Here are a few which you would frequently hear in everyday conversations. If you need more explanation on the usage of these expressions, don't hesitate to ask a Filipino friend.
Ay naku is uttered in frustration when things don't go in the way one wanted. Naku naman roughly means please don't do this to me. Nakupo is uttered in terror when something horrible is expected to happen or has happened. These expressions originated from the phrase inay ko which means my mother.
Asar naman (shortened form of nakakaasar naman) is an expression of disgust over how things are going. Asar na asar means so disgusted with and nakakaasar means it piques me when. The sentence, Huwag mo siyang asarin means don't pique or provoke her.
Basta (that's enough, I don't care anymore) derived from the Spanish word bastante. Basta on its own is uttered by a girl when she won't accept anything less than what is demanded. Basta na lang means haphazardly done. Hindi basta-basta means not of the ordinary kind.
Biro mo which literally means your joke actually means can you imagine that. Biro lang means just kidding. Hindi biro means it's not easy. You can say Hindi biro ang magpa-aral ng anak ngayon sa kolehiyo which means It's not easy these days to send a child to college.
When you want to say I don't know, the proper way to say it is hindi ko alam. But you can also say ewan ko which also means I don't know but with a subtle hint of and I don't care or and how dare you ask that to me. Ewan on its own is said when one doesn't really want to answer a question with a suggestion that talk about this topic be ended. Ewan ko ba expresses wonder or surprise at how things are going as in Ewan ko ba kung bakit mahal kita, a popular song lyric which means I wonder why I love you.
Sige from the Spanish sigue means goodbye, I'm going now. Depending on the context, it can also mean alright. Sige lang exhorts you to go on and not to mind if the speaker is left behind or no matter what happens to him. Sige nang sige means going on and on without careful thought of whether one is doing the right thing. Sige na means please and sige na naman means please, please, I beg of you.
Malay ko means what do I know about it in answer to a question asking what happened or where the hell is someone. This phrase is a bit charged with high emotional content and you can safely surmise that the speaker is agitated about something. Malay mo (literally what do you know) is used to mean who knows what good things are stored for you in the future. An example Tagalog sentence can be Malay mo baka tumama ka sa lotto which means Who knows you might win in the lottery.
When you want to say I wish, the formal way of saying it is nangangarap ako or minimithi ko. But nobody will talk with you like that. It is considered deep Tagalog. Colloquially, you use the word sana to impart the same effect. An example would be Sana magkabalikan na tayo which means I wish we could go back to as we were before (as sweethearts again).
Read my other article on frequently used Filipino idioms at: http://hinagapnikaure.blogspot.com/2012/01/frequently-used-filipino-idioms.html.