General Method Description

Smelting iron ore into iron bars is an excellent way of making money for low-level players, and also provides slow but steady Smithing XP as well. Unlike skills such as Mining, you smelt at "full speed" as soon as you reach the level you need, so this is a viable option even at level 15 Smithing.

Normally each iron bar has only a 50% chance of being successfully smelted, but with rings of forging that becomes 100% -- they should always be used.

You should complete at least the easy tasks of the Varrock Achievement Diary to get Varrock armour (any level), which gives you access to the furnace in Edgeville, which is the best in the game now that Jagex removed its annoying door. It is right next to the bank, and when wearing the armour you have about a 10% chance of smelting two bars at once, speeding up your Smithing by a decent amount.

Note that there is no advantage at all here to higher levels, so all the sub-methods are the same. Also, a beast of burden is rather pointless here, so at mid levels and above I recommend a foraging familiar such as a magpie, which will provide you a nice bonus in foraged items while you work.