Talking to girls is easy. It’s actually learning to take a hint and learn when women don’t want to talk that can be difficult. If you’re in a public place, and you see a woman with headphones on or talking on the phone or reading, this is often a good sign that she doesn’t want to talk. If she starts the conversation, just follow the flow.
When you talk to a girl - a woman, actually - you should try not to comment on her physical appearance. If you want to compliment her dress, her talents, her clothes, okay. But take a step towards “smile at me” or “hey (fill in with sexual insult here)”, you’re harassing her. This is not a compliment. Many women get offended, and they should. Instead of going down that road, ask her about her day, her life, etc. If she appears uncomfortable, change topics. It's not that complicated.