Best way to Find a password for a rar, zip

For example the file name is ProRat_SE_Fx18.zip

Go to google and search for ProRat_SE_Fx18.zip

you will get many results and read carefully...you will see the password

If u add pass after the file name ie, search for :
ProRat_SE_Fx18.zip pass

You will get it 99% of the time
Most of the times you can find the pass which is in this case

If suppose this is the last link of a file
http://rapidshare.com/files/142076077/BACKUPRBTS-sajid.part3.rar

then make link in this way and search it in google

files/142076077/BACKUPRBTS-sajid.part3.rar
or
142076077/BACKUPRBTS-sajid.part3.rar