How can I make lasting close friendships?

I'm shy but I'm quite good at making friends but keeping them is a problem, I think they get bored of me or only see me as an in school or reserve friend. I know you're supposed to ask questions but it can seem a bit nosy and how can I make myself seem interesting? At my old school the way to be more popular was to backstab and start arguments get people on your side then you've got some entertaining lunchtimes but that seems pathetic and immature to me. I've never had as good friends as I did in primary school when I had 2 best friends and we were so close and practically lived round each others houses but they both moved away :(. I'm moving for 6th form and I think most of my old 'friends' won't be staying in touch with me so what can I do better this time? What can I talk about when there's not much to say or going on?