If you don't want to be judged as a rapist, get consent. Real, meaningful consent. It's not that hard. "I'm attracted to you. I've been thinking about the possibility of sex. Are you interested at all? Can we talk about it?"

If you don't want to be judged as bad at it, then learn to communicate beforehand. "What kind of things do you like?" And be okay that, especially if you're young and inexperienced, you may not know what you like and don't like. Not every time you have sex is going to be good. That's life, there's a lot of factors at play. Don't look at your potential partner as a toilet seat for your sexual frustrations. Do your best to make it enjoyable for HER too.