When you are going for the interview either as a Salesforce Developer or Administrator make sure you know the answers for the questions given below.
1) What ia a multi-tenant architecture?
2) What are relationships in salesforce?
3) How many objects can be related with a Master-Detail relationship?
4) How many objects can be related with a lookup relationship?
5) Can you delete users in salesforce?
6) What is a page-layout?
7) What is a maximum limit of a Visual Force page?
8) What is a data loader?
9) What are the tools used for integration other systems[Oracle, Siebel etc..] with salesforce?
10) How many ways can you make a field required? What are they?
Salesforce Basics 