How to focus better with my Canon XTi and Tamron 28-75mm

[sinitry23]

I'm still a new to DSLR cameras and in need of your help. What can I do to improve my manual mode shots? Whenever I take pictures of the same object the manual focus I do comes out blurrier than the auto focus on the camera. It looks sharp and clear through the view finder but once I snap the picture and review it on my LCD screen all of the pictures that was taken manually seems a bit blur. The pictures I tested tonight was used on a tripod stand. What am I doing wrong? Are there any tips or tricks I need to know when manually focusing the lens?

Canon Rebel XTi 400d with Tamron 28-75mm F2.8 Lens.

Picture #1 was taken with manual focus.
Picture #2 was taken with the camera autofocus.
Both was on "M" mode.

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