The reason of talking to a girl is to establish a relaxed atmosphere and to be friendly. Thus don’t get involved into highly arguable subjects such as “Why death penalties for minors should be allowed” or “Why Greenpeace is doing more harm than good” or “Christmas has been invented by Satan, the Lord of hells” or something of that sort. Keep the affinity high and avoid “field mines”.
Moreover the No Sex Talks rule applies and that’s why you shouldn’t even mention words like “feminism” or “herpes” or “Islam” or “hemorrhoids”. Talking about “Why feminism is causing cellulite” OR “It’s a pity that there is no cure against hemorrhoids” OR the pick up line “Want some free breast cancer inspection?” is plain WRONG.