Their questions will be driven by two key things:
1. The job they are interviewing you for.
2. Your CV.
With regards to the job, make sure you read through the job description thoroughly and prepare yourself for questions based around that.
Also, go through your CV and refresh your memory as to everything you've mentioned in it - skills, responsibilities, the companies you worked for, job titles.
It would also be a good idea to do some research about the company. Have a good look through their website at the very least. Linkedin is another good resource for research. Look up the company and have a look at the profiles of some of the people who work there - including the people who will be interviewing you.
The better prepared you are, the more comfortable you will be in the interview.