Hi,
First of all best of luck for this step in your life. I hope you find someone really good.
Now coming to the topic, I can only say what I think are good qualities but obviously each person is different. In my pov the most important thing is theasy guy's nature and attitude. If he is not good looking or is fat etc that's pointless in long run. Life is a long time, he can loose the good looks, gain weight etc. However, the basic compatibility should be there which means that you are not repulsed by his appearance or either you or him don't match in looks. If one party is too beautiful, sometime negative feelings develop in other party because of other people comments or inner insecurities.
Next step is his family, they should be nice, good repute people even if you don't have to live with them. Ask around to see what people are saying. Try to take at least 3-4 people opinion.
After that see if guy is working or not. As long he is hard working even at a less salary he won't let you sleep empty tummy but if he is lazy person who lives off his parents even if they are rich than in future that may cause issues.
Religion,cast, education those are all personal matters which you and your family can decide according to your personal view.
Don't give too much dowry because that sets a precedent. In fact no dowry is best but that's not in our culture.
Last one , make sure to do engagement first and keep it for at least an year.this will give you all time to know him and his family better. Usually if there is something wrong it comes out in light.
These are some steps to be sure but remember marriage is a bet, one can never know. Be armed with patience,understanding and love for living a happy marriage. Compromises will need to be made and you may have to do it more in beginning but once you have settled in than things will work your way.
However don't stay in a relationship if he hits you or beat's you or if he has any bad habits because humans never change unless they want to change their own self. Never ever think that you can make him change or ''sudhar jaya ga'' of others. Don't expect filmy romance, romance yourself. Buy things, do things to keep yourself happy. Don't have expectations. This way if he does something you will be really happy but if he has serious nature than you won't be disappointed. Tell him you what you like in him repeatedly. Every human want to hear good things and then occasionally in private tell him if you don't like anything about him.same goes for engagement period. Don't involve other people in your personal relation. Keep it private.
I can keep on writing for ages and it will bore you to death. So ending it here.
Bye