The most likely cause of yellowed pictures is lighting.
Not enough or tungsten.
So you want bags of real light or artifical sunlight light.
Alternatively you can manipulate the photos but I personally find that harder.
The simplest way to get great light is to step outside.
You will find full on sunlight out a cloudless sky is probably TOO bright though.
So you want a cloudy but still bright day.
Set your camera to cloudy setting.
Set up on the patio table or something similar.
If you live somewhere that's always very sunny then make a light box. Google it, there's loads of tutorials and it's easy.
Another option is a windowsill.
You need cloud to diffuse the light but you're indoors so it's more convenient.
You don't even necessarilly need a little tripod.
My camera needs to be slightly above the subject to autofocus - resting it on a magazine does that.
The magazine edge is where I placed my camera.
Result:
I used a sony cybershot camera.
