From: crezzur
kill level 20 guards for clue scroll's ^.^
^ This if you do clue scrolls. Guards aren't that bad xp and level 2 clues > level 3 for being quicker to complete, and the fact that ranger boots = level 2 reward.
If you have 65+ ranged, you should complete Dwarven Cannon, buy a cannon, some cannon balls, and rather than meleeing green dragons, cannon them. Equip anti-dragon shield, the best d hide you can wear, your best melee or ranged weapon (depending on whether your strength or ranged is higher), games necklace (for tele to clan wars, then run east to drags), duel ring (to bank at c wars), and bring 1-5 food and 100-200 c balls with you, plus your cannon. Get more c balls from the bank when you need them, but don't take too many with you at once, and get your cannon set up quick in case you're killed by revenants.
You should make between 500k and 900k per hour in profit alone there. It's how I made 6M in 4 hours play only a few weeks ago (Was also flipping, a type of merchanting, which got me half of it. However you need 15M+ really to flip and make a good profit)
If I had the time to make a dragon cannoning script I would, as if you're using melee there, you should get 20-40K ranged xp per hour, around 15-30K melee xp per hour, and 500K+ profit. Making it possibly the most efficient thing you can possibly do on RS, aside from simply autoing ;)