Prayer

From Rs Wiki

Prayer is a easy skill to train for free players and members.

1.You can get bones from killing many monsters.

2.Once you get bones you can bury them by clicking on them.

3.Repeat.

Also you can use ecto if you are a member which takes a while but much more xp than regular but takes a while.

Bones can differ in xp like regular bones can give you 4.5 xp and dragon bones can give 72 xp.