I think the person may be talking about lifestyle issues rather than truly liberal Christian positions from a theological point of view (eg, one who does not view Scripture as authoritative on all issues).
Regarding the lifestyle issues, I will give it a shot based upon my experience. Not all of these will be held by all, but this should give you a flavor of some of the stuff out there.
1. Dress -- Women should wear dresses to church (or always), Men should wear coat/ties to church; No shorts ever - even in the back yard. Otherwise, you are a liberal.
2. Alcohol - Drinking wine and beer is a sin, and only done by liberal Christians. Sometimes even going to a restaurant where wine/beer is served(even if you are not drinking) means you are a liberal.
3. Entertainment - Those who attend movies, dances, etc. are liberal Christians.
4. Hair - Women=long; men=short; otherwise, you are a liberal Christian.
5. Music - Only certain types of music should be allowed in church. Only certain instruments should be allowed in church. Or, only certain music should be even listened to at all. For example, all popular (country, rock, etc.) music is sinful and only listened to by liberal Christians.
6. Jewelry - Women only for earrings (one per ear only), bracelets and chains. Men wear rings and watch only. If a man wears an earring, he's probably not a Christian.
I consider myself (and my church) to be fairly conservative, yet have been told that I go to a "liberal" church. Go figure. In any event, I hope that this helps. God's best,