Crafting is one of the 23 skills avaliable to all players in Oldschool Runescape. Players can craft, weave, create pottery, armor and spin with this skill. It is particularly useful to create higher level jewellery.
Crafting is also one of the hardest and most expensive skills to level to 99.
Quick Training Guide
1-10: Kill cows near Lumbridge with money in your inventory and tan them on the way to Al-Kharid bank. Completion of the quest Prince Ali Rescue is recommended. Make leather gloves until level 10.
10+: Buy a ton of flax and spin it in Lumbridge Castle, where there is a bank on the upper floor and a spinning wheel just one floor below it. Spinning flax is also a good profit, especially for starters, as you will gain around 40-60gp profit per spinned flax, along with 15 experience
Always try to maximize your experience gained per money spent. This exp/gp ratio will determine how much you will invest in training the skill. It is however not advised to grind on the most cost-effective methods if they take too long.