How do you get someone to open up to you?

So you know those people who you really want to talk to, and you can tell they really to talk to you too, but when you go out you have a lot of silences and things are awkward and you're just not hitting it off so you end up just staring and laughing at each other and talking about the weather? And then you wonder how you guys even because friends in the first place and its so unclear and you just really want this awkwardness to stop and you want to genuinely get to know your friend better but you don't know how to start?

[c=#7700B2][b]I have prefect duty with this friend tomorrow, so I get to stand in the same spot with them and pretend to actually care about the school rules for 30 minutes. Help me break the ice and this awkwardness?[/b][/c] Because as much I like hugging them and acting like super close, our word flow doesn't [c=#BF0000][i]flow[/i][/c] and it gets worrying like eventually things are just going to be genuinely awkward and I don't want things to get to that stage.

I don't have this issue with anyone else ok I really don't understand my situation. It's not like we don't have anything in common, but argh.