Helgafell is located on the Snæfellsnes, near the town of Hafnarfjörður. When driving on the 54, take the 58 in the direction of Stykkish. Follow the 58 North for only about 5km until you see the Helgafell sign on your right side. This road will lead you directly to the parking lot at the foot of small mountain. This is also where you'll need to pay for access to the mountain as it's private property.
The mountain became a sacred mountain in the times of the Vikings. When walking up the mountain you are not allowed to speak or to look back. At the top you make make three wishes and the might just be granted :) We were joined by two very friendly dogs on our way up.
Well.. it's not actually as easy as that, to see what you need to do exactly before making your three wishes see www.icelandicroots.com.