some people say “you just have that feeling that it’s the right one” but this DOES NOT HAPPEN TO EVERYONE, far from it. The decision has to be made with a lot of sechel, and be well thought out. Some people say, you know its the right one if you feel completely comfortable with the other person. (like you would to a sibling). Again, this works for some and not for others.
I would say daven hard that Hashem shows you if it’s the right one or not