Different hiking paths are available; the shortest and fastest start from the south, from Suðurstrandavegur, road 427. Other paths to the volcano are longer but nevertheless an interesting choice. Here it is important to protect the sensitive vegetation by following old riding paths and sheep trails.
The map costs 1500 isk. All profits go directly to the Icelandic search and rescue assosiation, Landsbjörg. You can pay for the pdf map directly to them:
IBAN: IS730370260268105301693759, SWIFT: ESJAISRE