One trait I most admire in my dearest friends is acceptance of others without harmful judgement.
I am slowly learning! I think the trick is actually to see the less obvious value in others: e.g. smart but uneducated. The hard part is that it is most hard to recognise ability in others in domains where I am relatively stupid.
Also I tend to try to have the less judgemental self-select towards me by giving myself traits that judgy plastic types (oooo ironic) don't like.
i am old enough that i managed to reduce judgement to one metric: is nice to other people. everything else is irrelevant when it comes to accepting someone as a friend.
for seeking a partner there are further questions related to compatibility of character and also goals, but that often is not what you look at when you are a teenager.
unless those restrictions prevent you from liking someone in the first place. i think young people do tend to make this mistake. i certainly did.