We cannot have one choice for this, it would depend on the familiarity of the person, the circumstances and the place. In some cultures a hug or a peck on the cheek is acceptable. In some, personal space is very important that getting too close or being over-enthusiastic etc can be frowned upon.
In most of my interactions at the workplace and job-related meets, it will be a formal handshake. Family and friends would be a hug. Elders and women apart from the above would be a namaste.
What is more important is not to overdo it and risk being misinterpreted, especially when it's people of the opposite sex. If you think back, most of the profession related handshakes are just a formality of a little/feeble contact. If you are in a position where you can do things for people, then the hands shake will be a little longer with vigorous shaking and profuse kind comments, if you are just a minnow in the hierarchy then it would be a mere touch for a couple of seconds.