Friendship takes work. Despite this, friendship can be lost as soon as one friend makes the other work harder in hopes of having the friendship proven. Friendship is about what you can do, not about what they did or what they did to you etc etc. Foremost, you have to have some meeting of minds, some shared sensibilities, interests, and/or worldview. Lots of differences will always be there. But some foundation for the friendship is needed. Then the differences can be celebrated, too.

I value lasting friendships. I don't mind knowing people for a short time. I don't cling to every person I meet. I don't even mind when a good friend goes away - moves for work, school, adventure. I would suggest, though, that close or not, the friendship is still lasting. I enjoy friendships that allow me to share my life changes and live through others' changes.

patience
Because people get lost. Friends go through shit that has nothing to do with you (and sometimes has everything to do with you). Let them go through it. Be ready to be there when they come out.

And get over the stupid things. I have been impatient with friends for being late. And I've heard other people go so far as to make declarations of morality concerning their pet peeves. But look: if a person is late, it doesn't mean that he/she has disrespected you, therefore does not value your friendship, and should burn in a lake of fire. If it is a consistent tardiness, don't assume he/she hates you. Get over yourself, and start showing up to meetings with that friend 15 minutes late.

(And in regards to those friends who are punctual: love them for that virtue.)

reservation of judgment
If you don't like somebody, that's fine. Stop being friends. You don't need to club them with words, just admit that you are different and move on.

But if you stay a friend, then hop off your high horse now and then to see what your buddy is going through down on the ground. When you eventually fall in the mud, they won't mind getting their hands dirty helping you up as well.

independence
I love my friends and want to be around them. And hanging in groups is good fun. But I am prone to private and sometimes intimate conversations with my friends. So if we are in a group, and I walk off with someone else for a while, don't cry like a child who lost its mother in the grocery store. Talk to somebody else. I neither hold nor wear leashes. (At least, not in platonic relationships.)

trust
Finally, after all the rest, you have to be able to trust a friend. Trust that the friend won't use you as his/her victim. Trust that they will be accepting of your differences. Good friends make the world feel more comfortable and orderly not because they slavishly agree with you or because they will follow you or because you follow them; good friends make the world feel more comfortable and orderly because they allow you to take a light look at conflict and realize that the differences and problems are only as heavy as their faces are long.

So probably good to trust that your friend can handle honest differences and conflict.