Obviously you can do a lot with your hands – but not during the interview.
To start with don’t flail your arms all over the place.Its a major distraction and its just not done. Even I have this habit. I used to take it along with me during interviews. To a large extent that explains my poor record in cracking interviews :-/.
Now, now let that not scare you from some genuine advice.
Coming back to the topic – some minimal movement is ok and unavoidable I guess.
Let it be firm.As firm as you can make it without hurting the other person.Firmness doesn’t mean stiff. A couple of pumps should do the job – convey the right message – that you are happy to meet the person. Even while shaking hands with women the same can be followed – you dont need to be extra soft – its not going to break.
the double hand shake is not advised – save it for a more personal gathering.