General Method Description

Blue dragons give guaranteed valuable drops in their bones and hides, along with other items on occasion, and a small number of Summoning charms. Because of the high value of their drops, they have traditionally been one of the most popular monsters for players looking to train and/or make money. At one time, it was very difficult to even find an "open" spawn to fight them regularly, but this has changed over the last year or so. It is now not difficult at all to find a dragon to fight, especially if you use the Ogre Enclave, which has six dragons. Since this dungeon requires the Watchtower quest to be completed, there are fewer players who can access it, and if you choose a relatively empty world, you can often find two adjacent dragons so you can keep fighting without having to wait for respawn.

At extremely high levels, I like to switch gears and take advantage of a couple of advanced abilities. I use super antifire potions (level 85 Herblore required) to allow me to make use of two-handed weapons, and then fight the dragons using Dharoks. This is not very dangerous (since blue dragons don't hit very often, nor very hard), and you can get a lot of kills very quickly. I combine this with the pack yak's Winter Storage scrolls to let me stay for a full hour per trip rather than having to run back and forth to the bank constantly. This is a trade-off, because the scrolls themselves are worth about 400 gp each, but the extra kills you get make it worthwhile.

Note that for the extremely high level method to work, you need to find a world where there are two free adjacent dragon spawns -- killing them is so fast that otherwise you'll be sitting around waiting for respawns.