To follow a god means to defend his philosophy and his honor against his enemies and help the other followers of your god. In this case 'enemy' is related to the relations all gods have to all other gods. If a god has 'good' relations to an other god it means they are 'friends'. If a god has bad relations to another god it means they are 'enemies'.

Gods doesn't accept as their followers characters with no or lame descriptions. See help description rules to get a catch about what description should like.

To become the follower of a certain god you will have to sacrifice bodyparts (arms, legs, brains, e.g.) of a follower (player or mob) of an enemy God of your chosen god to him at his priest in one of his temples.