In Christian Meditation, you focus on Christ and his teachings, and Christ's life. For example you could focus on the crucifixion and how much Christ suffered for us. Or you could focus on a quote of Jesus. In Yoga, you focus on your breathing, breathe in breath out, and stay focused on it and eventually you forget about the outside world until reaching a state of peace. Or you can focus on something; love, compassion, a mantra. I believe they are quite similar, in both you try to "reach God."