First of, REAL friends are hard to make, whether is in real life or in internet. Sure you can have many acquaintances, but real friends are hard.
What information is okay to give out?
When is it okay to give it out?
I was only able to make real friendship with males. And I only made a real connection when we exchanged skype. It's okay to give this information when it's pass several weeks, and you know the other person isn't a creep. When you can hear the other person, it's another level of communication. Typing is ok, but you really get to know who the other people are, his/her personality if you can hear their voice. I remember stuttering a little bit, not knowing what to say on skype, but the more time I gave, the better I talked. I had anxiety meeting people both on internet and in real life, but in the internet the anxiety was less intense.
What red flags do you look for?
Anything that the person say that goes against what I believe, not about religion/political stuff, but if the other person is a criminal, sounds like a criminal, or if the other person can't respect others or mine integrity (which I believe isn't right). If he/she sounds insane or is WAAAAAAY problematic/suicidal. Another red flag for me is if the other person like to blame others or me for whatever. Emotional immaturity from others I can't handle, it makes me run away, wheter on internet or in real life.
How long do you talk to someone before you consider them a friend?
Depends. I talk to some for years and I can't say we're friends. It's really about connection, how well you both click. Although this connection may take a while to create.
Any other tips/hard lessons learned?
I had a really cool friend from another state. I would say we bonded because we had the same problems with career, dating, finding a meaningful life, etc, even though he was NT and liked poetry and I liked math. But when he started dating in real world, got real friends, went to a great university, in a nutshell, fixed his life, he never went online again. I understand his decision, real life pleasure can be more enjoyable for some, and I'm glad for him, and miss him.
And I guess the most important thing is why?
Internet relationships have advantages and disadvantages. Advantages is there's billions of people you can find, statistically, by meeting people ramdomly, it's more likely to find someone more compatible with you on internet, due to more people are "meetable". There's less anxiety behind a keyboard. It doesn't drain all your energy, unlike meeting real life people.
The disadvantages is people can be really creepy behind a keyboard. The distance and time fuse can make communication problematic. And even if you both click, it's hard to give a hug (a thing I value in friendship) through thousands of kilometers of distance. Or hang out to bowling, eating, play pool, doing fun stuff that helps making a bond. Even if you're willing to invest time and money on travels, it's hard to hang out with internet friends. For some people they're not looking to hang out, but to me it's important, at least once per 3 weeks, on maximum once per semester.
So far, the number of real internet friends I have is zero, because we got busy with life and stuff, or maybe the bond wasn't so strong as I thought. But I had quite a few 1 year ago. But I still have some good friends from my high school, now that we went to the same university.
I know I forgot something, but screw it. That's enough of my experience and knowledge.