In its hutch your guinea pig should always, always have access to plenty of hay - they eat this (it helps their digestion) but they also like to play and hide in it. Make sure there is a covering on the floor of the hutch, like sawdust or wood pellets. When handling the guinea pig, pick it up with one hand under its bottom, the other under its shoulders so you don't hurt it. Sit down when you cuddle your piggie and stroke and talk to it lots. They like to feel secure. Do this regularly, and it will soon know and trust you and will be comfortable in your company. Most of all,guinea pigs love company - and this is what makes them feel happy.
If you have an outdoor piggie, bring it inside or into a garage or shed in cold weather.