It's quite normal to be nervous before an interview, but there are a few things that you can do to help prevent you from sweating profusely and shaking during an interview.
1. Get a good night's sleep before the interview.
2. Don't alter daily routine just because you have a big interview.
3. Remind yourself that the employer must like your qualifications; otherwise, you wouldn't have been asked to come in for an interview.
4. Remember that the fate of the world doesn't rest on this one opportunity.
5. Don't drink too much coffee! Not only will it make you hyper, you may want to visit the restroom more than normal.
6. Consider exercising prior to your interview. If you can go for a run or get in a good workout, you will get rid of your excess nervous energy.