Here check it out
https://valheim.fandom.com/wiki/Skills?so=search

From what I understand, skill raises exponentially, so the higher your skill levels are, the harder it is to improve them. If you really want to level some basic skills quickly is using an item such as a boulder. You can swing any weapon against it and it will improve your skill with each hit. For skills such as running and jumping, you can improve your skills by running into a wall or just jumping in place. For blocking, just letting a Neck of Greyling hit your shield constantly is a quick way to improve the skill. Good luck!

Xp is gained per "action"

each swim stroke
each hit with the ax or pickax <multiple numbers show = multiple hits = multiple xp>
each jump
running I assume with each step
bow skill is hit with arrow

Amount of damage does not matter

a "hit" is something that does damage... a 0 will not progress skills. <it used to but they stopped that so people wouldn't stand there hitting rocks all day>

Originally posted by GunsForBucks:

Xp is gained per "action"

each swim stroke
each hit with the ax or pickax <multiple numbers show = multiple hits = multiple xp>
each jump
running I assume with each step
bow skill is hit with arrow

Amount of damage does not matter

a "hit" is something that does damage... a 0 will not progress skills. <it used to but they stopped that so people wouldn't stand there hitting rocks all day>

My bad, wasn’t sure if that had been taken out as I’ve never really used it. Another interesting strategy to gain skills if you have two players online is you turn your PVP on while their PVP is off and hit them with any weapon, those weapon skills will increase.

I don't think there's accounting for area hit. When blocking/parrying the parry is usually better. Check the wiki for the details as every weapon/shield has potentially different responses. May you be blessed with rapid leveling :-)