Skills level up as you use them, and each feeds the others.
FarmingTilling, sowing, watering and harvesting on the farm alm.
WoodcuttingFelling trees for wood. Spruce grows everywhere; birch on the forest alm.
MiningBreaking boulders and ore: stone and quartz at first, copper and tin later.
FishingCasting into streams and pools, and holding on when something bites.
SkiingRiding your own slopes, carving, braking and taking jumps.
MeleeFighting up close with a stick or a better weapon, in the deep forest and the mine.
ArcheryFighting from a distance with the hunter's bow.
Farming: tilling and watering tire you less, and a harvest may give a second crop.
Woodcutting: swings tire you less, hit harder every third level, and may give an extra log.
Mining: swings tire you less, hit harder every third level, and may give an extra lump.
Fishing: casting tires you less and the catch zone grows.
Skiing: you ski faster.
Melee: blows tire you less and hit harder.
Archery: shots tire you less and hit harder.