Nail file, not rasp:
Start by finding the right kind of file for the job. Do not raid the tool box where you keep hammers and nails. A two-sided file is best with one side being super fine grained and the other a little coarser.
Most nail professionals recommend a nail file that has a foam centre but you can use any two-sided nail file that you prefer. Whatever you do, resist the temptation to use the coarse side of the file on the top of your nails.
Do not use sandpaper and stay away from metal files which are really meant to be used on artificial or acrylic nails. Remember to replace your files when they start to show wear in order to prevent breaking your own nails.
It is all in the angle:
Remember to protect yourself from injuring your nails by using the proper angle to shape your nail ends. Keep the file at a 45 degree angle to your nail tip.
The biggest concern many have with keeping their nails healthy is determining which length they should keep. The most important determinant for this is personal activity first and foremost.
If you are someone who rarely get their hands wet or dirty, who do not do any labor that requires grip strength, then you can keep your nails as long as you like.
Most people opt for keeping their nails a quarter-inch long to allow them greater flexibility and ability to use their hands. If you frequently use the keyboard, you know how frustrating it can be to be trying to hit the keys on one row and finding that they are hitting the next.
Optimally, you have to care for your nails on a daily or every other day basis, which would prevent you needing to clip your nails. However, if you do not have the time to do this, and your nails do happen to grow past a half inch length while you are away or busy doing other things, take some time to clip your nails.
Just make sure that you do it properly. Start at the side of the nail and work toward the middle on either side. Then if the nail has not already come off, use the clipper to remove the middle, letting it come off on its own. Never pull or tear. Then remember to file your nails so that they can look and feel their best.