how to level up

Short answer - give away games.
Detailed answer - FAQ

to elaborate smokys reply:

you level up by giving away games yourself. Specifically ... games that have "value", aka Contributor Value (CV)

the base worth of a game is decided by the base price (not the discounted price) in the US steam store.

BUT... if the game or rather keys to a game have been given away for free at some point in time, those games when given away wont add to your Contributor Value.
Games that have been bundled only add 15% of their Base price to your CV = Reduced value
additionally games that have been heavily discounted will also be count like a bundled game.

to know if a game give full CV, reduced value or 0 CV, you can go to the Giveaway creating page and type in your game. before choosing/clicking on the game you will see a drop down with possible choices based on what you typed in. there you might see games with or without asterisks** at their name.
no asterrisk means the game gives full value, 1 means it gives reduced value and 2 means no value. that way you might know beforehand how much CV you will receive.
but be aware: the list for reduced and no CV (bundled and free games) that the system takes reference, is being managed by hand, so they might not be completely up to date

Kill monsters.

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