Number 1- Treats!
As any Guinea Pig owner would know, the quickest root to a Piggie's heart is through their stomachs! They love veggies and will do anything to get them! Try to give your little friends a treat every time you pick them up or go to their cage. This way, they will learn to associate you and being picked up with all good things!
Number 2- Be sure of yourself.
Guinea pigs don't often enjoy being picked up (I mean, would you be? A giant hand coming from the sky to grab you?) so make sure when you do, approach them slowly but surely. Make sure you are comfortable with picking them up and holding them. If you are afraid to hold them, so will your piggies! Your guinea pigs can sense your nervousness and it rubs off on them!
Number 3- Hold them properly.
The correct way to pick up a guinea pig is with one hand under their stomach, just under their front legs, and one hand under their bum. Hold them against your body as soon as you can so that their feet can feel something solid. This gets rid of their feeling of falling. Make sure you keep at least one hand on them (under their bum) to keep them steady at ALL TIMES. If you hurt them whilst holding them, it can cause a lot of distrust that will take a lot of time and treats to fix!
Number 4- Spend time with them.
Although sitting outside of their cage and talking to them is a good way to get them comfortable around you, it's not enough. To properly bond with your guinea pigs, make sure you put aside some time in your day to take them out of their confined area and let them run around freely. They can choose if they come to you or not and eventually they will! Just make sure that the place you let them run around in is secure and has no dangerous objects. I'd also suggest putting down a towel or fleece as they might stain your carpet with pee!
Number 5- Socialising
If possible, keep their cage in a room where you spend a lot of time. This way your piggies can get used to the sound of a busy house. This can make them more accustomed to humans if they see them all the time.
Number 6- Understand their behaviour.
Guinea pigs are very easy to understand if you know their behaviour. They are very vocal animals and will tell you if you are hurting or scaring them! So pay attention to their body language and sounds and you should know what your guinea pigs are thinking!
Number 7- Their Environment
Creating a safe, comfortable cage for your guinea pigs is one way to indirectly earn their trust. If your piggies are happy, then they are more likely to be happy with you too! If the cage is too small or you haven't cleaned them out for a while then they aren't going to be happy with you, trust me! Remember to add toys into their cage to keep their brains and bodies occupied!
Number 8- Be kind.
Guinea pigs startle easily so go slowly around them. Always be kind to your guinea pig. Never punish them for wrong doings, especially not by shouting or withholding food. This can lose you all the trust you had gained. They will likely remember this and you will be back to square one!
Number 9- Get them a friend.
Guinea pigs are very social animals so it is imperative to get them in pairs or even more! They are herd animals and feel safety in numbers. They are more likely to adjust to their new environment a lot better with a friend for comfort.
Number 10- Be patient.
The final tip is a very simple one. Be patient! Every single piggie is different; some may take a month to trust you, some may take years. It all depends on the guinea pig. Just never give up on them. They will come around eventually and don't get mad if they run away. They are prey animals by nature.