Depends on who is paying. If your office is paying, they would advise you. If you are paying for the ticket(s) travel agencies and online booking sites can be a cheaper option. Most travel agents pass on their percentage to the customer so just 'MAY BE' cheaper. Check with an airline for a particular destination and then check with at least two travel agencies (don't worry, they usually answer the phone). Research, research, check your research and then do some more research ... then go with your gut feeling!