Infinite dataset

[fidoboy]

I want to implement a infinite data set using ajax, do you have any tip or advice about where to start? I'm a bit lost. My idea is initially load -1, 0 and 1 index, so when user switch, for example from 0 to 1, i need to destroy -1 and using ajax, load the item index 2. Or in reverse way, if initially user moves from 0 to -1 i need to destroy 2 and using ajax load -2. I suppose that you get the idea...