Requirements while installing patch

HI Exports,

                              I am using sap Bo 3.1 sp3   ..Now we are planning to install sp7 patch . .

        My Queris:

                        . Before installing ,we need to follow any  steps.like(Need to install sp3 or sp4)

                              . How to install patch and after installing we are going face any issues  ?

                               . IF we are facing any ,issues how to over  come this issues 

Requirement:

                               .  Could any one share some documents and links

Thanks,

Raghunath