I'm a strong believer of online connections. Getting your work seen is important. Meeting new people, who are creatives like yourself, is important. Asking people for advice is important, but... there's a huge difference between saying "give! give! give!" and saying "Hey, this is what I just did for you, keep it up"
Approaching people online requires a skill, but I think it also requires that you give a damn. Because if you don't care about the person you're contacting the odds are they won't care about you. Fine, if you're contacting 100 million people, and you get 0.1% who say "okay, I'll do this for you" then you've amassed 10K people. But DO YOU contact 100 million people or is it more like 100? If the odds remain the same, none of the people you reach out to will do anything for you. So, here's a concept:
"Hi" - that's right, I've received messages like this. Yes, the entire message was just "Hi". My initial response is "What do you want?" My secondary response is "If you don't care to write what you want right away, then I won't ask you for it" I know it's the easiest two letters you can send somebody, but if it's a person who could make a difference for you, you might have just made a big mistake.
"Can you look at my XYZ?" - this is when people fish for comments, likes, followers, etc. When you do this, you right away are saying: hey, I don't know you, you don't know me, but do me a favor. It's literally like begging for money on the street. Most people feel uncomfortable, others don't care, and a small amount will feel sorry for you enough to do you a solid, but... again, you might be missing out on some valuable connections.
"I'm an XYZ, how can I help you?" - better, but... you are making it sound like you want to help them, but in fact it is you who's looking for help. This might have worked in the 90's when people didn't know how internet works. If you're reaching out to people, they will assume you want something from them, not the other way around, that's why it's better to...
"Congratulations on your XYZ. The part I liked the most is XYZ. What made you do XYZ?" - that's right. You just liquored them up, and ended up with a question. Notice that there were no "I's" in this message, other than the "I liked that..." part. Now, if this person cares enough to respond, they will do so, but the odds are much higher that they will answer your question that has something to do with what they did, because you took some time to research and find out that they did what they did. It shows respect. You learned something about the person, and possibly, if you ever run into them at a party, there's a conversation starter free of charge. Best thing - if they decide not to respond, that doesn't mean that the bridge is burnt. They won't associate you with the beggar on the street, or someone who has very small vocabulary. Here are other do's:
"I just watched the film XYZ. I saw that you were credited for XYZ. It's hard to believe that you did that when XYZ. How was it to be working with someone as amazing as XYZ?"- this might apply to most of your industry contacts. IMDb is your friend. Read some bios, and check some credits.
"I just gave you thumbs up on your youtube video XYZ. I thought it was remarkable. Do you have anything else in this genre?" - again, good for new filmmakers, or somebody who's promoting themselves online. If you want reciprocation, the best way to do it is to do something first. Statistically, if you follow somebody on Twitter, the odds that they will follow you back are about 1 to 5. The odds that people will follow you if you open a Twitter account and do nothing with it? 1 to, umm... let's just say their slim to none.