In my case usually me and my new italki friend are interested in knowing each other. It means that we are asking questions about our countries, families, hobbies. Then we are talking about English ("How long have you been learning?" and similar). Sometimes people are interested in starting relationship. I do not like this kind of italki users as in my opinion it is not a dating portal ;-)

People like to tell about themselves. It's an universal law :-) Start from favorite movies, books, music, food...With time it'll be clear what's ok or wrong to talk about.

We talk about work/study, customs, events in our lives, what we did on the weekend etc.

damn.

Our life, what we've been up too recently, culture and customs in our worlds, and politics.