From campus placements and Technical Interviews you will need to brush up your programming skills in C and C++ (most important) and Java. You will also need to brush up the basic concepts of the core subjects of Computer and IT Engineering syllabus, namely - DBMS, Operating system, Computer Networks and SQL. Preparation level required for these subjects depends from one company to another. A few companies who offer you an annual package of more than 5 Lacs will definitely expect you to have sufficient skills so as to match the offered profile.
For rest of the companies, basics of C, C++, Java and or SQL is more than enough.
For preparation of these programming languages you can refer :
For revising C Language , go through
Let us C - Yashawant Kanetkar