Couple things to keep in mind.
0. Do you know
how to hold your camera?
1. Is your shutter speed fast enough? (camera shake blur)
2. Is your camera focusing where you want it to? (AF system, using a single AF point)
3. Are you always shooting with your lens wide open? (stopping down to f/8 can increase sharpness).
4. Are you shooting with the sun at your back, or are you shooting into the sun?
5. Are you doing any post-processing?
You may also want to read
How to take sharp digital photos and
how to tell the difference between motion blur and misfocus.