Be skeptical of any travel agent or company who contacts you cold. If you haven't given out your information to this specific travel company, then chances are that these people are calling you and thousands of others with the same lame story about how you have won a certificate for a free cruise.
Assume that any telephone solicitor who asks for your credit card number over the phone is a scammer. Unless you have initiated the call and are familiar with the company, keep your credit card information to yourself.
Make any checks for vacation travel payable to a known and reputable company name. Be very wary of any travel agent or company who requests that you make a check or money order payable to an individual.
Run far away from a high-pressure cruise salesperson. Be particularly skeptical if the salesperson tells you that you have to make a decision about the cruise on the spot.
Check whether you can purchase the same cruise at a similar price from a reputable agency. If not, then you're likely dealing with a scam artist.
Proceed with caution if the company requires you to select several departure dates in the future, or if you must wait until a later date to travel.
Ask whether the travel agency belongs to any known organizations like ARC, IATA, ASTA, ARTA, CLIA or NACOA. A legitimate agency belongs to at least one or two of these associations.