Sit by his cage and talk to him. Give him a little treat from your hand if possible. Give him lap time each day. Whenever you do something for his cage like veggie time, make it a big deal, let him hear the veggie bags russle, and when you give it to him, make a big announcement. Anytime you interact with your piggy make it exciting. This way they get to know your voice and that you represent something good. Whey you give him hay, announce it "Time for some hay" and russle the bag and give him hay. Your piggy will soon associate the different sounds for these good things and will start to get excited. This has worked for me.