Gently push your cuticles back following a shower or bath. You may do this with a towel while drying them, or use an orange stick with a little cotton wool wrapped around the end. Be gentle or you will damage them. Never cut your cuticles - leave this to an expert with a regular professional manicure.
Dry your hands and nails thoroughly before attempting to file your nails or you may damage them. To keep your nails at their strongest, file in one direction rather than using a 'sawing' back and forth action, which will make them weaker and more prone to breakage. Avoid acetone- and formaldehyde-based nail varnish removers and stick with acetate-based removers instead, which are gentler on the nail.
When painting your nails use a base coat to avoid staining or weakening the nail. Try a strengthening formula such as Sally Hansen's 'Diamond Strength Instant Nail Hardener'.