Why do I get a blurry photo when I set my lens in manual mode?

When you're composing your image, slow down a bit and get a sharp focus on your subject. If you're into portrait photography, try keeping the subject's eye in focus. If you're using a handheld camera, then even with a sharp focused subject, the slightest shake introduced during pressing the shutter button can cause image blur. In this case, try using timer mode to let the camera take the photo automatically. Finally, try using a stable tripod and a cable release or a wireless remote that will eliminate any chance of shake with hand touch.