Context matters considerably...
When first meeting someone there are little signs of interest that are similar regardless of orientation. Are they checking you out? Are they flirting with you? Believe it or not LGBT+ people flirt in much the same ways that straight folks do, we're still humans after all.
It sounds like you're questioning your sexuality, or thinking about exploring, or expressing it, perhaps for the first time. That's great and I'm happy for you. Here's a few pointers that may make it easier to meet like minded people:
There are most definitely places you can go where it's fair to assume that most people are not-hetero. Consider going out to LGBT+ bars and clubs, or a local Pride event. Many larger cities also have LGBT+ community centers and organizations (some organizations specifically cater to teenagers and young people)
Try to get a handle on your sexuality, and/or what sort of people you would like to date, before you start experimenting. At least try to keep in mind that the person who you end up experimenting with is a person with feelings. It's heart breaking to start a relationship with someone, only to find out later that they were just trying something out. Try to be honest with people, and your self, about where you're at.
Take things slow. It's easy to fall for the first person who accepts your sexuality, particularly if you're not out and feel somewhat isolated. There are still plenty of fish in the sea, even if/when you're LGBT+. Date around, find someone you really love and want to be with.
It's also worth noting that sexuality is a spectrum. People aren't necessarily straight, gay, lesbian, or bisexual. Many people fall somewhere in between, some people prefer not to date at all. It's a spectrum not a team to join, don't be surprised, or worry, if you find that your interests aren't what you thought they were or that they change over time.
Lastly... Enjoy your journey. It may seem strange and scary right now, but it doesn't have to be like that. Reach out. Find people in your community that have been where you are now, there's a huge loving community of LGBT+ people out there that are trying really hard to make it a little less strange and scary for people like you.
These are just starting points. After a little while, of spending time with LGBT+ people, you start to get a feel for what people are into. What initially feels like taking a big risk in asking out the wrong sort of person slowly diminishes, and even if/when you misread someone, it doesn't feel like a big deal.
I guess there is such a thing as "gaydar" but I assure you that it isn't a super power... It's just something that you begin to notice with practice and spending time with LGBT+ folks. Like I said it isn't a super power, it isn't magic and sometimes your instincts may be misguided, so don't rely on it entirely.
When in doubt, ask. If you want to ask someone out on a date, ask them out on a date. Seems a little obvious, I know, but it's the only foolproof way to know for sure if someone wants to go out on a date with you.