Mission impossible here as everyone of us is different meaning each of us has a visual image of our Mr Right in our minds and there is no way of telling what the image is. The biggest thing here is trust your gut instinct as the heart has been known to and does lie, be friends first before anything else and if someone seems to be too good to be true, chances are they are so be careful. Also if meeting someone online, remember that anyone can be anyone they want at anytime on here so meet in a public place for the first time with a friend nearby just in case but don't let on and if you have any doubts , no 2nd date and never give out your address or telephone numbers on here til youre absolutely sure, but be willing to take a chance in love just like in life. Good luck and be safe
Some things that might be important long term, no right or wrong answer but these things can/will impact you if you are in a relationship with them - their motivation level (ambitious? Lazy?) education level (employment outlook), their personal beliefs (religion, etc) How they feel about kids (some don't want any, some definitely do - can be a real deal breaker) How they handle their money (saver vs. Spender) Any addictions (drugs,alcohol, etc) How they keep their home (neat? Slob? People don't generally change this, just be aware)
You'll know if this is the right person for you, you won't need to consider anything.
However, if you want to think about the character of someone you're thinking of as a possible relationship here are the three things I would recommend.
Sense of Humor
Shows respect to you.