How to store iPhone contacts if I change my phone?

So I have an iPhone4 and will be using a Samsung Galaxy S4 now, is there a way to store all my contacts so that I won't have to add them all over again on my S4?
Please keep in mind I'm not very technology savvy so step by step instructions will be greatly appreciated!

*My iPhone does not have any Jailbreak and it's ios is up to date.

IPhone Wi-Fi is slow and I think I know why but i have no solution?

I went on my computer and went to my router's home page. I went into connected devices and deleted my phone from it. Now it's slower than ever! I use the fastest Comcast internet available and before my phone was faster than light. Other phones connect and have amazing internet. I connect to other networks in other places and works awesomely. My phone now won't even load anything.

Could it still be usable? (iPhone 5C)?

Okay, so my friend is going through a hard time and well to shorten the story her phone bill got out of hand and her phone is being shut off. I offered a little trade, her iPhone 5C for my iPhone 4. My iPhone 4's contract ended, so the phone should be good to use still.

Now I know when an iPhone gets shut off the EM-something number is reported bad, which doesn't allow anybody to activate that particular iphone. Now I only want to basically use her phone as an iPod/Web browsing (connected to Wi-Fi of course.) my question is, Could I still be able to use her iPhone as an iPod?

Why won't my iPhone play videos on Instagram?

So I have a iPhone 4 on net 10 prepaid with unlimited talk, text, and web. But every time I try to play a video on Instagram it won't work? It loads for about 5 seconds n then it's just froze with a circular arrow(The Retry or refresh button) but everything works on Wi-Fi. Does anyone know wats the problem? I tryed rebooting my phone n updating instagram n my iPhone but still.

How to Factory Unlock My iPhone 4S on iOS 7?

I have Verizon, but where I'm I don't get very good service. I want to use AT&T. How can I factory unlock my iPhone 4S on iOS 7? F0recast also said there was a factory unlock.