Pay-to-play Smithing training

Quests Rewards
Total: 49,482 Experience
 * 1,000 - Recipe for Disaster
 * 2,257 - Heroes Quest
 * 2,500 - The Giant Dwarf
 * 5,000 - Between a Rock...
 * 5,000 - Elemental Workshop I
 * 6,500 - Devious Minds
 * 7,000 - Cabin Fever
 * 7,500 - Elemental Workshop II
 * 12,725 - The Knight's Sword

Levels 1-29
The Knight's Sword is a free-to-play quest that gives 12,725 Smithing experience upon completion. This reward would elevate a level 1 Smithing to level 29 immediately. It is strongly recommended that people interested in Smithing do this quest as soon as possible.

Levels 1-15
Bronze bars provide 6.2 or 12.5 experience. Smelting 1 to level 15 would take around 389 bars whereas Smithing would take around 193 bars.

Level 15-35
At level 15 you can smelt iron. However, players only have a 50% success rate when smelting iron. Players are able to achieve 100% success if they are wearing a ring of forging, using superheat magic or use the Blast Furnace located in Keldagrim. (~12.8k experience/hr and ~120k profit/hr at 100% success rate; ~6.4k experience/hr at 50% success rate)

Level 19-35
Alternatively, at level 19 members can make 15 iron nails from an iron bar. It is possible to make 900 iron bars into 13,500 iron nails per hour at a leisurely pace. This method provides ~25k experience/hr, which is more than double the experience from smelting iron bars.

Level 34-54
Buying steel bars from the Grand Exchange and smithing steel dart tips (10/bar) is a good way to train Smithing as the buy/sell process should break even or make a profit. You have to complete The Tourist Trap to do this, though. (~33k/hr) 34-54 smithing will use 3,905 steel bars.

Level 35-99
Smelting cannonballs from steel bars is extremely profitable however very slow experience. To smelt cannonballs, players must complete the Dwarf Cannon quest. Each steel bar gives 25.6 experience and 4 cannonballs. 507,704 steel bars are required to achieve 99 Smithing. (~14k xp/hr at a rate of about 540 bars per hour). Alternatively, players may smith iron nails for increased experience but decreased profits.

Level 40-99
Smelting gold bars is a relatively quick training method for Smithing. This requires Goldsmith gauntlets from the Family Crest quest. The gauntlets increase the base experience of 22.5 to 56.2 experience per bar. 231,268 gold ores are required to achieve 99 Smithing if using the goldsmith gauntlets.(~300k xp/hr)

The fastest way to gain xp is at the Blast Furnace, it is possible to gain upwards of 320k xp/hr. This has been the reported maximum experience per hour using the TrueBF group.

This method, as of July 2016, costs around 7 to 7.5 coins per experience.

Level 54-74
Making mithril dart tips is a very good way to train Smithing, both due to its low cost and decent experience. This requires partial completion of Tourist Trap and 54 Smithing. 1 mithril bar used (which is around 1,200-1,350 gp) gives 50 experience makes 10 dart tips which sell for 135 coins each instantly. This method is very afkable, a profitable or break-even alternative to smelting gold ore, and decent experience (~52k xp/hr if paying attention). Doing this method from 54-99 would require 257,672 mithril bars.

This method, as of July 6th 2016, loses about 0.6gp/xp

Level 74-99
When you get to level 74 Smithing you should start making adamant dart tips instead of mithril dart tips. 1 adamant bar will give you 62.5 experience. This is around 60k xp/hr. Doing this method from 74-99 would require 191,011 adamant bars.

Smelting
Players can smelt ores into bars at a furnace for Smithing experience. Alternatively, players can superheat which allows players to smelt at a bank or at a mine for the cost of 1 nature rune and 4 fire runes. Players only have a 50% chance of smelting iron ore at a furnace unless they use a ring of forging or use the superheat spell.

Some players turn steel bars into cannonballs at a furnace after they have completed the quest Dwarf Cannon.

Players who have completed Family Crest can use Goldsmith gauntlets to increase the experience for smithing gold ore from 25 to 56.2 experience. This is one of the fastest ways to gain Smithing experience.

Smithing
Players can choose to smith bars into armour and other metal items at an anvil. Traditionally the best things to smith are iron knives and platebodies, depending on whether the player wants fast experience or profit.

Blast Furnace
Players can play the minigame Blast Furnace to smelt ores using half the required amount of coal. There are friends chats that provide free services for Blast Furnace, making it wildly popular as a method for training and a method of money making.

Other

 * Another great way to gain Smithing experience is at the Motherlode Mine. One can world hop and repair the two broken struts in the center of the Motherlode Mine, an effective method of training Smithing for Ultimate Ironmen. Repairing one strut awards the player with 1.5 times your Smithing level in experience. At a good world hopping rate one can gain upwards of 45,000 Smithing experience per hour.

Furnaces

 * Al-Kharid by the bank
 * Edgeville no longer requires completion of the Easy Varrock Diary, however there is still a 10% chance of smelting two bars at once while wearing Varrock armour.
 * Falador Square
 * Neitiznot north-east from the bank chest. This is the closest furnace to a bank. However, The Fremennik Isles has to have been started to use this furnace.
 * Port Phasmatys directly across from the bank. This is the second closest furnace to a bank, with Neitiznot being the better option.
 * Lumbridge near the general store.
 * Wilderness Resource Arena.
 * East Ardougne next to the church, south of the north bank.
 * Shilo Village next to bank

Anvils

 * Across from Varrock West Bank.
 * South from Yanille Bank.
 * North of Falador, east of Taverley, Doric's hut after Doric's Quest.
 * Northern hut of Tai Bwo Wannai.
 * Port Khazard has a bank near it now but is still inefficient for smithing.
 * Northern West Ardougne.
 * South-western Rellekka.
 * West of the Ranging Guild.
 * Nardah.
 * Wilderness Resource Arena.
 * Void Knight Outpost.
 * Blast Furnace