A fast and easy way to train in prayer is to go to somebody’s house in Yanille and use their guilded altar.

You see when you get to a house with a guilded altar you just right click on the bones you have then select “use” then use the bones on the guilded altar by clicking on it.

The guilded altar gives 350% of regular experience (when burners on the sides of altar are lit). WITHOUT the burners being lit, you get 250% of regular experience (50% extra for each)

If you want to light the burners by yourself you need to use a tinderbox and 1 merrentil to light one. (yes the merrentil does disappear once used)