It takes patience and real trust in God in order for you to know this. It we sincerely seek God's direction in our relationship and patiently trust Him after a while we will become sure of His will. It's a deep thing so it is hard to explain but if you are close to Him you will understand and be sure. I hope this helped.
That is a good question. What we Nazarenes do..... our potential partner must be Torah observant, That is first and foremost. By keeping Torah, this proves their fear, love, and obedience toward Yehwah. Second, its time to get to know their character, and see if you are compatable in that area. Things ya'll like to do, etc. Just ask Yehwah for wisdom and understanding, and He will give it to you.
Very late response.
The truth be told, there is really no 'right' person.
Every marriage is the product of its environment. Shared space, values, interests, groups,etc. will bring people together and when wisdom is applied to demonstrated interests, a decent and fulfilling marriage may result.
This assumes that there is enough commitment to the person, the marriage and the institution.
Very often, the marriage itself makes the right person(s) of the parties involved. Opportunity more-so than inclination, is responsible for the success that we all yearn for, in our family life. The accumulative effect of the choices we make, tell for win or woe, in our spousal connection.
So 'how can I tell that I have found the right person to marry'? Risking the time and energy to develop a bond with someone with whom you share enough 'common space'; someone whom you experience mutual TRUST, RESPECT and with whom you are willing to COMMIT.
Still seek God's wisdom to see beyond the facade of courtship.