Hello there,well there are numerous ways to get ready for any job interview,any way a person feels comfortable.

1)This is a common routine.I don't think he will be given time to actually leave and think about the offered position.But he will be given some time,say a few days to respond to the company about his decision.
2)There aren't any in fact,with regards to attending a job interview and negotiating the salary,there are cultural sensitivites and guidelines that he should adhere to though as long as he stays here.
3)Yes there are,he can start off by going a bit over the offered pay,and explaining well his past experiences and actually bieng able to convince them that he actually does deserve a higher pay.
4)He should expect benefits and opportunity for growth within the organization.
5)This is a tricky question,the best way to answer this is that it would be a lot better if there was someone inside the organisation he knows well,he in turn would be able to 'squeeze' the best out of the company,in terms of bargaining and other issues.Another option is he has to be himself,with his own power of persuation and negotiation,these are good times for the country so they would obviously oblige!
I hope i helped you with these tips.Take care.