Blacksmithing is one of the professional manufactures in WOW. Players can use blacksmithing to craft weapons or armor gears. Also, can craft the mount Steelbound Harness. These can be sold in the auction house and get a lot of WoW Gold. 
Recipe for the skill of blacksmithing before 700 can get from blacksmithing trainer. So it makes very simple for it before 700. You can use the material of the old version to get to 700 quickly. Some of the Recipes maybe need you to do reputation or quest, but the gears crafted by these will be very cool, it's good for illusion.
After version 7.0, Recipes can get by professional quest. What's more, there are different rank for the different recipes. Only can be upgraded by the quest to improve the rank of the recipe. Before 780 is easier, after 780 most of the 2-star recipes can't level up the skill of blacksmithing. So how to improve the rest 20?
First, you can get Recipe: Demonsteel Waistguard - Rank 3 by Sightless Eyes. This recipe you need to farm a lot of Blood of Sargeras. If you have enough Blood of Sargeras you can get to 800 quickly.
Second, When the reputation of Highmountain Tribe is exalted, buy Recipe: Demonsteel Armguards - Rank 3. This recipe only needs a few Demonsteel Bar, but the reputation of Highmountain Tribe to exalted takes about 3-4 weeks. Of course, the other faction to exalted also can get Recipes. But it will cost more wow gold compared with Recipe: Demonsteel Armguards.
You can choose to get 800 quickly or let the reputation to exalted then leveled up to 800. Both are OK.

Tips: When the Darkmoon Faire come each month, you can level up 5 profession points leveled up by quest. You can decide how to use this opportunity best.