A farmer is only as good as his or her abilities allow, and in Stardew Valley that's where Skills come into play. Split into five different categories, Skills roughly describe how good a character is at doing a particular thing, whether it's splitting rocks, chopping down trees, or hewing monsters in twain. Skills are developed by doing things, simple as that. You do those things, you gain experience, you get better. That's Skills.

Each Skill has ten levels of proficiency. At each new level your character will improve their abilities in one or more tasks, as well as learn how to Craft new items. The more you engage in an activity, the faster your Skills will grow. New Skill levels are acknowledged when you sleep each night. It should be noted, however, that your Skills will grow during the day - you're just not told you've levelled up until you go to bed for the night.

When you reach level five in a Skill you'll be asked to choose a profession. Your profession will give you bonuses specific to one facet of your skill - for example, if you reach level five of Farming you can choose between Rancher or Tiller, which give bonuses to money earned from animal products and crops, respectively.

Farming

The Skill you're most likely to develop on a daily basis. Farming can be levelled by creating and maintaining anything related to your farm, such as tilling fields with your Hoe and watering crops with your Watering Can.
  • Level 1 - +1 Watering Can Proficiency, +1 Hoe Proficiency, Craft Basic Fertilizer, Craft Scarecrow
  • Level 2 - +1 Watering Can Proficiency, +1 Hoe Proficiency, Craft Stone Fence, Craft Mayonnaise Machine, Craft Sprinkler
  • Level 3 - +1 Watering Can Proficiency, +1 Hoe Proficiency, Craft Bee House, Craft Speed Gro, Cook Farmer’s Lunch
  • Level 4 - +1 Watering Can Proficiency, +1 Hoe Proficiency, Craft Iron Fence, Craft Preserves Jar, Craft Basic Retaining Soil
  • Level 5 - Choose Profession - Rancher (animal products worth 10% more) or Tiller (crops worth 10% more)
  • Level 6 - +1 Watering Can Proficiency, +1 Hoe Proficiency, Craft Hardwood Fence, Craft Cheese Press, Craft Quality Sprinkler
  • Level 7 - +1 Watering Can proficiency, +1 Hoe Proficiency, Craft Loom, Craft Quality Retaining Soil
  • Level 8 - +1 Watering Can proficiency, +1 Hoe Proficiency, Craft Oil Maker, Craft Keg, Craft Deluxe Speed-Gro
  • Level 9 - +1 Watering Can proficiency, +1 Hoe Proficiency, Craft Seed Maker, Craft Iridium Sprinkler, Craft Quality Fertilizer
  • Level 10 - Choose Profession: If Rancher - Coopmaster (befriend Coop animals more quickly, cut incubation time by half) or Shepherd (befriend Barn animals more quickly, Sheep produce Wool more quickly); if Tiller - Artisan (artisanal good worth 50% more) or Agriculturist (crops grow 10% faster)
Foraging

The act of stripping the wilderness of its resources. Foraging can be levelled by gathering items in the field, but you're most likely to develop this Skill by chopping down trees.
  • Level 1 - +1 Axe Efficiency, trees sometimes drop seeds, Craft Wild Seeds (Spring), Craft Field Snack
  • Level 2 - +1 Axe Proficiency, Cook Survival Burger
  • Level 3 - +1 Axe Proficiency, Craft Tapper
  • Level 4 - +1 Axe Proficiency, +1 Wild Berry Harvesting, Craft Charcoal Kiln, Craft Wild Seeds (Summer)
  • Level 5 - Choose Profession - Forester (Wood worth 50% more) or Gatherer (chance for double harvest of foraged items)
  • Level 6 - +1 Axe Proficiency, Craft Wild Seeds (Fall), Craft Warp Totem: Beach
  • Level 7 - +1 Axe Proficiency, Craft Wild Seeds (Winter), Craft Warp Totem: Mountains
  • Level 8 - +1 Axe proficiency, +1 Wild Berry Harvesting, Craft Warp Totem: Farm
  • Level 9 - +1 Axe Proficiency, Craft Rain Totem
  • Level 10 - Choose Profession - If Forester - Lumberjack (normal trees sometimes drop Hardwood) or Tapper (Syrups worth 25% more); if Gatherer - Botanist (foraged items always gold quality) or Tracker (forageable items revealed)
Mining

Once more unto the depths. Mining entails pounding away at rocks for the valuables contained with in, and levelling is typically achieved by smashing stuff with your Pickaxe.
  • Level 1 - +1 Pickaxe Proficiency, Craft Cherry Bomb
  • Level 2 - +1 Pickaxe Proficiency, Craft Staircase
  • Level 3 - +1 Pickaxe Proficiency, Cook Miner's Treat
  • Level 4 - +1 Pickaxe Proficiency, Transmute (Fe)
  • Level 5 - Choose Profession - Miner (+1 ore per vein), Geologist (chance for gems to appear in pairs)
  • Level 6 - +1 Pickaxe Proficiency, Craft Bomb
  • Level 7 - +1 Pickaxe Proficiency, Transmute (Au)
  • Level 8 - +1 Pickaxe Proficiency, Craft Mega Bomb
  • Level 9 - +1 Pickaxe Proficiency, Craft Crystalarium
  • Level 10 - Choose Profession: If Miner - Blacksmith (Bars worth 25% more) or Prospector (double Coal found); if Geologist - Excavator (double Geodes found) or Gemologist (gems worth 20% more)
Fishing

Heeeeere, fishy, fishy. You can level Fishing by cruelly pulling aquatic life from its watery home with a fishing rod.
  • Level 1 - +1 Fishing Rod Proficiency 
  • Level 2 - +1 Fishing Rod Proficiency, Craft Bait
  • Level 3 - +1 Fishing Rod Proficiency, Craft Crab Pot, Cook Dish o’ The Sea
  • Level 4 - +1 Fishing Rod Proficiency, Craft Recycling Machine
  • Level 5 - Choose Profession - Fisher (fish worth 25% more), Trapper (resources needed to craft Crab Pots reduced)
  • Level 6 - +1 Fishing Rod Proficiency, Craft Spinner, Craft Trap Bobber
  • Level 7 - +1 Fishing Rod Proficiency, Craft Cork Bobber, Craft Treasure Hunter
  • Level 8 - +1 Fishing Rod Proficiency, Craft Worm Bin, Craft Dressed Spinner, Craft Barbed Hook
  • Level 9 - +1 Fishing Rod Proficiency, Craft Magnet
  • Level 10 - Choose Profession: If Fisher - Angler (fish worth 50% more) or Pirate (chance to find treasure while fishing doubled); if Trapper - Mariner (Crab Pots never catch Trash items) or Luremaster (Crab Pots no longer need Bait)
Combat

Smash! Combat is levelled by killing monsters in the Mines with a weapon. Pretty self-explanatory.
  • Level 1 - +5 HP, Craft Sturdy Ring
  • Level 2 - +5 HP, Craft Life Elixir
  • Level 3 - +5 HP, Cook Roots Platter
  • Level 4 - +5 HP, Craft Warrior Ring
  • Level 5 - Choose a Profession - Fighter (all attacks deal 10% more damage, +15 HP), Scout (increase critical strike chance by 50%)
  • Level 6 - +5 HP, Craft Slime Egg-Press, Craft Oil Of Garlic
  • Level 7 - +5 HP, Craft Ring of Yoba
  • Level 8 - +5 HP, Craft Slime Incubator, Craft Explosive Ammo
  • Level 9 - +5 HP, Craft Iridium Band
  • Level 10 - Choose Profession: If Fighter - Brute (damage increased by 15%) or Defender (HP inreased by 25); if Scout - Acrobat (special move cooldown cut by 50%) or Desperado (critical hits kill)