5. Use a Metal Nail File
Never 'saw' back and forth and always file in the same direction for each hand. For your left hand it's important to file towards the left and for your right hand file towards the right.
It's a good idea to file on a slight angle for the sides of the nail and create a nice arch at the highest point (like this: up, across, down), this will make your nail an oval shape which is ideal for preventing chips and those dreaded 'splinters' and hang nails which you ultimately have no choice but to cut.
Use the pointed tip to get dirt and other gross things out from under your nails. You should do this regularly to keep them clean and healthy, but is especially true for those with long nails!