Help!! I don't know how to prepare for the TOEFL

Hi everyone
my next test will be on Oct 13, 2014
I need at least 79 to be accepted at university ugh..
2nd time my score was 63 R8,L11,S22,W21
3rd time my score was 78 R17,L17,S22,W22

I took the test last week but it was too difficult so i don't think i will make it in my 4th time
I prepared for the toefl last time by using
notefull 3steps toefl mastery,longman prep ,and delta's toefl prep

The only section I'm confident with writing but I don't know what to do with the other sections
What should I do to get 79 ??
I'll be grateful to you guys