Finding a Life partner

If you're not someone already in love how do you find the right person for you?

How do you people define what are your non negotiables while finding a partner? What criteria do you define? How do you pursue the conversations? How to know what to look for in a relationship? How to identify the red/green flags in minimum conversations to not get played with?

Especially how to navigate through dating apps or matrimonial sites where you just have an online view of the person.

Kindly suggest if you've gone through any of such processes and could successfully get to a state of marriage. Would appreciate view point!