There are several ways that you can use to magnetise an ion nail. For instance, you can magnetise it using an electric current, through the use of induction. You can also stroke it with either the North Pole or South Pole of the magnet. You can also strike the nail with a hammer, while holding it parallel on a magnetic field. The blow will overcome the resistance of the domains movements and line up to the earth filed, causing the nail be magnetised.