Define “ideal.” Too often people define ideal in terms of physical attributes (height, body type, age) which leads to a narrowing of the pool. Instead, focus more on the characteristics of the person that truly matter. Do you share core values, do you laugh together, how does the person treat others in the world?
Discuss the basics with a partner early on; do you want kids? How do you handle finances, spiritual/religious positions, and expectations? And what are your political ideologies? You do not have to align on all of these but mutual understanding and respect are essential.
Laughter is key. Find someone you can laugh with, someone you truly find funny, and you will have the #1 relationship sustainer.