Looks? Or Personality?

Looks at first because you both need an initial attraction(wanting to kiss), but defiantly long term personality starts tomatter more (unless its a horrible personality right awaywhich would be an extreme).

But what defines a good personality, probably its how it mixes with yours. A good example would be are they too different than you or too similar. Too much you'll clashlike a reclusive introvert and a crazy extrovert, or you die of boredom because you're hanging out with a clone.

To figure this out itdepends on you finding out or knowing your own temperament, how much are you willing to tolerate, and how much can they tolerate you. This might be 80/20, 50/50, or 30/70... if that 30% is really wonderful.

Recommend to learn about the big 5 personality traits, find out what you are, and get good enough to noticeother peoples personalities. This will help you not wasting your time and others because you could've been to talking with someone special.

Or if you don't have time for that the quick and dirty way is just figure out how you relate to someone, because you can't talk to someone if you can't relate on anything, but at the same timewhat you don't relate on might be potential to show interest to learn and create a relationship.

Ranting done, good luck out there.