Final Year Engineering Project: How to choose project Guide ?

In our earlier postings we had covered different aspects of final year projects such as

• For Final Year Project : The Purpose, 
• FInal Year Project,
• Know Your Engineering Self  .
• Final Year Project Work: Seeking senior's input

Another equally important issue here is choosing the guide for your projects. Here are some questions u might help us answer.

• What is the importance of a project guide?
• How can he help us in our project? or What help can we expect from him? How to choose a project guide?
• What if guide is not expert in the area of projects ?

Your answers help juniors make good choices?