This. A skill is increased by using it - in the case of combat skills, you need to use the skill on a valid opponent. In the case of crafting skills, more powerful potions/enchantments and stronger weapons/armour increase your skills more than weaker types.
I guess this is why my friend told me to put on every necklace, ring, bracer, armor and drink everyone potion available when you do your smithing. I guess it gives a larger quantity of skill points. But you'd have to find activities you can do often, like smithing or alchemy, because when I go on a mission/quest I usually shoot my bow about 10 times if I'm lucky, so that's not gonna go very fast. See what I mean?