The charities have a lot of information on their websites, below is some general advice to help you get those needles clicking.
It can be a great asset for when the child becomes a teen as this is usually a time when there are many differences between the parent and the child. Any kind of needlework which you share can help to eliminate differences, tensions, and arguments, and bring you closer together.
The blocking mat is another accessory that can be extremely helpful for the knitter or crocheter, or even for those who enjoy sewing and quilting. This mat serves for pinning the project to its surface, making it very easy to line up the project, keeping straight edges, hems and seams.
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.
The charities involved usually have free knitting patterns and advice on their websites so do not be worried by all the details as you really will be able to find a garment to suit both your knitting skills and the babies needs