The charities have a lot of information on their websites, below is some general advice to help you get those needles clicking.
First and foremost it will be a great way to spend some quality time with your son or daughter. (Yes boys can work with yarn too!)
Yarn: Premature babies have very delicate skin and can often be allergic to wool; therefore it is best to steer clear of garments made with a wool mix. Acrylic yarn is more appropriate when knitting for preemies. Ideal yarn to use for preemie knits is baby double knit or 4ply yarn. Most preemie patterns will use these.
Engaging children in needlework is a great way to keep them from being bored and occupy them for hours! It’s very cheap too, especially when comparing it to other activities which they may enjoy. Young children or teens won’t be able to work as fast and therefore one project will keep them busy for a while, thus saving you money.
Next it will keep them from watching so much television or playing video games. It could also save you money on snacks, as that usually goes hand in hand with television. This will result in more active and healthier children, as junk food causes obesity, and other health problems, and deprives the youngsters of energy. Plus too much television is bad for the eyes and mind! Needlework on the other hand is good for the mind as it keeps the mind busy.