What makes a good friend? Is it remembering events and occasions, sending cards/flowers/gifts, remembering details about your life? Or is it something more simple?

To me, the best measure of a good friend is being there to listen without judging. Everything else is just icing.

Not every recall of events mean he/she is a good friend.
some people do it just formally.
i think a good friend is someone who's there for you no matter what and someone who cares and shows interest about you.
also someone who talks frankly and doesn't envy you.

Depends on what you want I suppose. Some people want shoulders to cry on, some people want others to enable them, some people even want those who will fight them back. To me, it's all about finding someone who will compliment you, meaning they will complete you in ways you cannot. My girlfriend's best friend is opposite to her in a lot of ways but at the same time, they share a lot in common. So I guess what I'm trying to say is that friends are basically the siblings you weren't born with. You can fight with them, laugh, share experiences and learn from one another and no matter what happens, you'll still love each other.

Mmm, but sometimes a little judging is good, depending on definition of same. A true friend who has your back instinctively (my own best definition) will pipe up when s/he thinks you're going to rip your parachute -- no?

good call. Yes a good friend will also say the things you need to hear, when you need to hear them, and also know the difference between when to say what you need to hear, and when to say what you want to hear.

I suppose it goes both ways but that describes what I'd look for in a girlfriend more so than a friend. Again they cross over in many or most ways.

I think I'd like to have more in common than uncommon with a best friend. Recalling events and crazy stories that happened between us is icing on the cake for me. I like being friends with people I can relate to and enjoy combing our efforts to have fun together.

A best friend is someone who you can share a car ride with without saying a word simply because you enjoy their company. A bit extreme to some but nonetheless. I believe a best friend is a person who will never betray you, a person whom with you would charge the enemy in the trenches, a person you would buy another round for, a person you would walk home under the shoulder when they're too drunk to walk.

That's sums it up for me.

I don't know a specific single characteristic because the people I consider as my great friends exhibit different friendship behaviors for me. One thing they have in common though, aside from willingly sharing part of themselves to me, is they can be 'disturbed' any time of the day without making me feel like I have disturbed them. There is sincere interest and deep conversations, not just casual bored talks.

Even if we haven't spoken for a long time, when we finally talk it's as if there was never that time gap that passed. The connection doesn't get old and I'm confident that it will be the same several decades from now.

I can relate with this. There's something comforting about just knowing that the friend is present that we don't really need to talk (and not talking doesn't create a feeling that something is wrong either).

I think that a good friend is someone that is always there for you no matter what. I have recently lost a best friend because his girlfriend doesn't like me hanging out with him! He said he has to stop talking to me to save their relationship :(

For me it's someone that is going to be there when you really need him or her. I don't mean why you need a favor or anything of that nature, I mean something serious happened to your life and you that friend will be there no matter what.

Like the quote goes (and I'm paraphrasing here):

A friend will bail you out of jail, a best friend will be next to you in the cell saying, "That was ****ing awesome!"