Nikon set up

[kramnosbig]

Hi all
Please can anyone offer any advice.
I have been taking pictures of my kids playing football and cricket for ages.Recently I
decided to take my hobby on to the next level in order to produce better quality results.
I am using a Nikon 300s with a Sigma 300 mm f 2.8 prime for cricket and football.The trouble is I am struggling to get real pin sharp images.The images are ok but not muck better than when taken using a lens a fraction of the cost of the sigma.
Could anyone offer any advice as to the set up of the camera please.

[chris-p]

Can you post some examples of whats "not sharp"?

Also, what AF settings are you using, and what aperture are you shooting at? You ought to be getting pin sharp results with that sort of kit but the depth of field will be tiny at f/2.8 at 300mm so you could just be focusing poorly.