My boys wear white shirts and polo shirts for school and if you know anything about my boys then you know that Mini is just noise with muck on.
So I work hard at keeping my whites white and avoiding that greyish tinge that they can get. I used to be pretty picky about what I used when the boys were smaller and you would often find a bucket of clothes soaking prior to washing in a baby friendly solution in my downstairs loo.
I find that the key is to keep to a routine now and to not expect a miracle they are never going to be whiter than white, but they are not grey either!
Make sure you sort effectively
One stray coloured item will render a whole wash slightly tinged!
Pre Treat oily body marks with a bar of soap or stain remover designed for whites. If the stain is particularly fixed use an old toothbrush to scrub it.
Add a laundry booster
I do this for the boys shirts every half term. You increase the cleaning power of a detergent by adding a booster, such as borax, oxygen bleach, or washing soda to help maintain whiteness. I am a fan of Dr Beckmans products
Tackle colored stains.
Address food spills, such as coffee or juice, and underarm yellowing, which is residue from antiperspirant or deodorant, by applying undiluted liquid oxygen bleach directly to the fabric immediately before laundering.
You will be amazed at what effect the sun can make on stains and keeping your whites looking bright.
Martha Stewart has a really cool stain remover checklist that I keep in my laundry area.