Food
Guinea pigs love fresh vegetables and fruits of all kinds. Just make sure that you are not overfeeding your guinea pigs, and use fruits and vegetables only as treats.

Otherwise, you will want to feed your guinea pigs specially formulated guinea pig pellets, which are available at pet stores and cost various prices depending upon quality. You might want to ask the store or breeder where you got your guinea pig(s) from what they have been feeding them, so you have one less thing to worry about, and one less big change for the guinea pig.

You will also need a daily supply of Timothy hay to help aid in digestion, also available from pet stores.

Other care
An annual check up at the veterinarian should be enough to keep your new pet healthy and happy, but if you ever see any trouble signs with your guinea pig, such as not eating, contact your veterinarian right away.

For more on guinea pig health issues, please visit this great site:
http://www.guinealynx.info/