Guinea pigs do best when kept with another guinea pig.
Guinea pigs are social animals, and live in colonies in the wild. Domestic guinea pigs do best when living with at least one other guinea pig as a cage mate.
Guinea pigs get along best when both small pets are spayed or neutered. Have your guinea pigs altered before you introduce them to each other.
Before putting two strange guinea pigs together, let them get to know each other first. Start by keeping them in separate cages and placing the cages next to each other so they can see and smell each other. Leave the cages like this for a week or two until the guinea pigs seem comfortable with one another.
Next, let them come face to face in a guinea-pig proofed room or cage that is not familiar to either one of them. This neutral ground may help them from becoming territorial with each other. Once the two are getting along well in this situation, you can start keeping them together.
If you only have one guinea pig, spend a lot of time with your pet since you are its only source of companionship. That means you should hold your small pet and play with it every day.
If you have more than one guinea pig, be sure to spend individual time with each of your small pets to help them bond to you. Although they have each other for companionship, they will appreciate having a relationship with you as well. If they are bonded with you, they will be more comfortable being handled.