I need help about harry potter sooo all you fans answer this!!?

i am going to c the midnight showing of harry potter and the half blood prince on Tuesday (technically Wednesday) and need some help/advice. I have only read books 1 and 2. I saw all the movies but started to get confused a little in the 3rd 4th and 5th movies. i want to know what harry's current status is....his situation with voldemort, with the dursleys, dumbledore, the ministry of magic, hagrid, sirius black. What actually is the order of the pheonix (never figured that one out). in general what is the 6th book gonna be about?? is there anything that i missed that is key in the 3,4, & 5 books that they didnt put in the movies...HELP! Should i try to watch movies 3 4 and 5 again?. Look at summaries?