well, since this is a language learning site, it's best to discuss first your interest about learning languages. next would probably be about your life or family nad so on and so forth. It is actually you who will decide whether the topic is ideal to discuss or not.

To me, any topics will do except my personal matter, about politics, religion

The topic of weather is always safe.

But we need to say more, we need to tell a nice story- something we fins interesting. The question I asked my students is "What's cool?" "What are you into?" "Any hot tips?" "I love manga" "I build and race sailboats" "I love the ballet, I just went last week to see the Pacific Northwest Ballet, it was great!" "I've been going to see this band, the Tone Kings at Moe's saturday nights, they're awesome, check it out!" being an enthusiast of something shows your passion and shows you in your best light, and it doesn't matter whether we care about your thing, we enjoy your brief description. So if you can ask that question, that topic is always welcome, and brings up the best in your acquaintainces.

This is a very good question! Of course it depends a lot on the person and the situation. Different topics are welcome or expected, but a lot depends on social class and age or maturity. For instance, in the US a good topic among working class people is sports, but if the team is local or the event is big the interest may widen to everybody. Movies and music are good topics with college students but middle aged people may not spend time on either as work limits their time. I think a major real difference- something that tells me something about the quality of the person I am talking to- is their outlook. Do they like to complain and talk about bad things, or do they like to talk about good things they like? Does their question have too much bragging (or the opposite- self deprecation?) When I was a teacher every term I would ask each student to introduce themselves. Being young, they had not yet learned how to do that. They'd say their name and look puzzled. So I would ask them questions they should have answered as a self-introduction: My name is... I'm from... I do ... (major in school or profession) You should be able to say that in a sentence or two. Don't tell a long story! give them a chance to take you in and have the impression that they would like to hear more. I'm Zooey, I'm from Seattle, and I'm a retired teacher.