do you want a youngster or an adult?
a pet?
a show cavy?
a house cavy?
a breeding cavy?

When you have taken these into account and got all the equipment that you need I suggest that you contact a local breeder. Cavy Breeders may advertise in your local ad mag or newspaper. If there are no breeders local to you or they have nothing to suit your needs I suggest that you try the following website http://www.cavies.net/ or http://www.cavybreeder.cjb.net/ as they both have a breeders directory and sales page.

When you have found a suitable breeder, go along and see what they have for sale. When you are choosing you cavy check:

~their coat is clear from mites and bald patches
~it appears fit and healthy with bright eyes and a healthy coat
~their teeth are not broken or maloccluded.
~it doesn't have diarrhoea (could indicate further problems)

One point of note is that all cavies have a bald patch behind their ears this is nothing to worry about and your young cavy may well be a little nervous to begin with. The young cavies should be at least 6 weeks of age.

Talk to the breeder about your preferences and he or she should advise you. If you are interested in showing or breeding a particular breed it is a good time to ask about the breed in question and ask about good and bad points of the breed.

Once you have choosen you cavy settle it in when you get home and leave it to be (apart from feeding etc) for the first two days so it gets used to its surroundings.