Referring to romantic love, though I believe there is much overlap on the topic.
I have not found much in the way of solid advice on how to find the right person to be with. And after many, many mistakes, I am starting to become of the mind that most successful don't know why they are successful and have little experience, and those with much experience are likely to never commit to a point to make it work, despite having more understanding. It's a bit grim, but I guess it is what it is.
Firstly, I think few are ready to share their life with others. Improving yourself is a never ending process and you are tested in far more ways than you'd ever imagine being in a romantic relationship. At the end of the day you can only change yourself. Be prepared to do that... a lot.
Secondly, try to have enough attention from the opposite sex that you know what it looks like and you don't fall for someone just because they are the first person to bat their eyes at you. This may not be an issue for most, but I think it is for some. It's good to feel like you have options and thus you feel more confident about holding high standards. But don't be cocky about it and use that to feel that others are disposable. It can be a thin line between confident and knowing you are attractive to some and being completely self absorbed.
What makes a couple click?
I think many things work and don't work. I have experienced first hand what it's like to be with someone who you admire and who is good to everyone except yourself. I've also experienced a great deal of compatibility and situational convenience without being on the same wavelength. And lastly, I've begun to understand what it's like to be exceptionally compatible with someone but in a very difficult situation outside of our relationship, all around.
There are many things to consider. One is the practical side. What would a relationship with this person look like? In your words, and in theirs? Where are your differences in those ideas? Are they 30 miles away? How flexible are they in life? Are they 3,000 miles away?
In another aspect, are they independent? Can they tell your parents about you? Are they in control of their life? How many things do they have on their must-do list that don't or and probably won't involve you?
Are they philosophically and idealogically compatible? This might mean neither of you care much about such things. It might also mean that you are very opinionated and open minded. Or it might mean that you are both fairly closed-minded but have very similar views.
Do your goals in life align? Can they align? Will your goals draw you further apart or closer together?
How close of a relationship do you want? How physical of a relationship do you want? How do you receive love and how do they?
How much do you enjoy a casual conversation with your date? How much do you enjoy being around them with others?
How well do you work with them at your lowest points? How well do you work together at your highest points?
Do you feel relaxed around them? Could you spend day after day with them in your life and not grow tired?
I think all of these things are extremely important to consider. But also that it's a bit of give and take. It's very possible to have a lot in common with someone on paper. Same interests and goals. But then find it a challenge for one to keep up with the other, being on a different wavelength. I think it's extremely important to be comfortable with someone. It's not bad to have to adapt some, but if naturally you find their company enjoyable but draining or boring and comfortable, why bother? I think it's good to have a large focus on finding someone who you enjoy being with even in the dull moments. Life is full of dull moments.
It's easy to take someone on dates, disconnected from the rest of eachother's lives and have a good time -- whether you are rather compatible or not. I think it's no magic to fall for someone on a cruise or dating only on Friday nights. It is much more special to fall for someone over the little things. Conversation over a walk, over a longer period of time. When you're stressed, when they're stresed. Getting along in the good times is much less notable than getting along in the average and bad times. Couples don't break up at their best moments -- it's at their worst.
I do think situation and independence is important to have figured out before hand. But if you find someone truly special who you admire, enjoy, who helps you grow, and you are passionate about, if you aren't willing to have some inconveniences in your life then you probably aren't ready or they aren't the right one. On the other hand even a brilliant relationship can be stressed to the max if other elements of life do not line up. It could be one person working too many hours or being far apart with little opportunity to connect. But life situations can change. General chemistry is unlikely to change.
I would highly recommend dating very casually, seeing others as friends. Not getting attached or romantic until the basics have been worked out. But also not being overly pessimistic. If you're pessimistic you're both more likely to miss what's in front of you and to scare away what could be in front of you. But if you are overly optimistic you are just going to get hurt and hurt others. It's a bit of a balance and a struggle that no one probably has the right answer to.
On the same topic, the world seems to be deluded on the topic of sex. You have many people waiting till marriage, while trying to walk the line as precisely as possible over terminological exactness. If it's not intercourse you can't get hurt from it, right? Absolutely false. Sex starts to happen very shortly after the most simple of kisses do on a scale. I am not saying kissing can get one pregnant, of course. But that the one can easily turn into the other. And that may be okay, but I would caution most not to wait till marriage for sex but to wait a longer time before kissing and making any notable physical or non-physical sexual contact. Perhaps a candid conversation on the topic to determine your desires in the area, but I think it is likely better to sleep with 5 people than mostly do the act with 20.
A good relationship requires a lot of introspection and understanding. It's good to be able to understand your weaknesses and why you do things the way you do them. And always improve them of course, but know where you are likely to make mistakes and why. If you feel the relationship is a bad idea or you think it's a bad idea, it probably is. But if you think and feel it's a good idea, you have a slim chance. In general your odds are slim and it's important to realize that. But part of what makes love special is the uniqueness. Falling for someone at the wrong time and the wrong place, but who you can't stand to be without. Falling for someone who will steal your shoe and play with you rather than giving you a dumbfounded look when you try to do the same.
There's a lot of must-haves and then there's a lot of wiggle room. I think no one knows who will be perfect for them. And I think the person perfect for you probably doesn't also have the easiest situation to work with yours.
I've barely scratched the surface but I hope this helps someone. There's much to ask and consider.