What does it mean when a guy tries to teach you something, like how to play a video game or a guitar? Is it just friendly, or could it mean he likes you? Or... is it just showing off?
You folks probably know how I think by now. I think everybody likes everybody, at least if they're teenagers, and if a boy successfully manages to get out of bed and arrive at school, I'm inclined to say it's because he is hopelessly in love with you, whoever you are. But I'm going to try my best to look at this objectively, and give you an answer that applies to all dudes, and not just the ones who think like me. I'm aware that some guys claim they have tons of platonic female friends (though frankly I think they're lying out of their big fat incorrect mouths). So here's my impartial take on some situations like yours, and a verdict on whether or not the dude engaging in them likes you.
1.) Teaching you stuff
This can be a purely friendly gesture. On one hand, and I am not being sexist here, it's cute when a girl is like "How do I video games??" and attempts to play them anyway. I assume the reverse situation is also true, like when a girl tries to teach me how to sew, and I'm like "Aaaah what do I do, which part of the needle am I supposed to accidentally stab myself with?? OUCH, THAT PART, OKAY GOOD." There's nothing demeaning or belittling about this; it's just that there's always some uncertainty when people don't know each other too well—a sense that everyone is always putting his or her best foot forward—and it's humanizing, and comforting, when someone is instead like "ACK, HELP."
So in that sense, it could just be a fun, friendly kind of thing. But let me ask you this: can you picture him treating another dude the same way he treats you while he's teaching you something? Because in my experience, a guy doesn't sit there with another guy and teach him guitar chords and tell him he's doing great. In my experience, a guy goes "Hey, learn to play guitar so we can jam sometime. Like I jammed with your mom last night." And then he goes "Oooooh" and punches the other guy in the head. There's a good chance that "my experience" was just the experience of having terrible friends, but you get my point. If he's being all helpful and caring, this is more than just a friendly act. (Furthermore, "just showing off?" Showing off is often a pretty good sign he cares what you think about him!)
2.) Inviting you to a really big event
Verdict: Not necessarily.
If a guy invites a hundred people to a party, and mentions it to you too—"Hey, I bought a metric sexload of Cheetos, I hope you come to my house and eat them"—he is not necessarily in love with you. Of course, he might still invite a girl he did like in the same offhand way, just to act casual, but the point is that the invitation by itself doesn't mean anything, and you'd have to look at his other behavior.
3.) Inviting you to a really small event
Verdict: Yes necessarily.
This covers everything from "My three friends and I are going bowling, you should come," to "Let's go have coffee! Kissfully." If a dude only invites a few people to do something, and you're one of them, you're either pretty close friends or he wants to put his mouth on your mouth in a non-CPR context.
4.) Making an isolated comment about your (music/clothes/phone/something)
Verdict: Probably not.
I bring this one up because I've apparently misled girls this way. Someone will play a cool song on a jukebox, and I'll be like "What was that cool song you played on the jukebox," because I genuinely want to know, and then I'll walk away, and she'll assume that meant "We should take off our pants in a room sometime." I'm not saying that the girl in this situation would be wrong to misunderstand me—nobody is wrong, because everything is confusing and life is a hopeless mess. I'm just using this example to illustrate that, while commenting on your (something) can be flirtatious, a dude who comments on that thing and then leaves you alone might just have cared about the thing.
5.) Frequently talking to you about nothing
Verdict: Totes deffs. (By which I mean yes.)
If a guy is constantly asking you about the geometry homework you both have to do, he could like you, or he could just not understand what a triangle is for. But it's a different story if a guy is constantly like "Hey! How's the, uh, things, of the world. How are those things. It sure is... raining today! ...Oh jeez it has actually stopped raining, I am so sorry." Blabbering like a moron is a sign of nervousness, and people don't get nervous around someone whose opinions don't matter to them. Granted, maybe the dude is just plain awful at talking, but that still wouldn't explain the "frequently" part.
6.) Flirting with you, then ignoring you
I realize that women sometimes flirt strategically in this way, to pique a guy's interest, but guys (well, sincere guys) don't. If a dude is like "You have pretty eyes and an acceptable butt and you are soooo smart" and then later he ignores you entirely, he's doing the romantic equivalent of fly fishing. He is casting into the stream of ladies over and over again to see who bites. No guy who genuinely likes the genuine you would decide to start ignoring you unless you somehow did something to provoke it (but that is a whole other ball of canned worms).
7.) Texting/chatting late into the night
High school guys need more sleep than anybody except literal babies and they never ever get enough of it. If a dude is staying up really late to text back and forth with you, and you're all "LOL my dog ate my whole burrito" and he's like "OMG really??" he's not literally beseeching God because of your burrito-eating dog. He is caring about you.
And that's the main thing to look for, both in the "teaching you stuff" situation and in all of the rest of them: are you just another bystander in this situation, or is he paying particular attention to you? And more importantly, is he being friendly with you, as he might be with another guy, or is he being more considerate and attentive than he is with everyone else?