most times I leave them alone, and RARELY go past new _____ as a matter of fact, the first time i ever went beyond that was my first game when i had a huge pangea with 1 other civ and got up to New ______ 4... i don't remember what civ I was... it was probably zulu or babylon... i didnt know the differences between the civs, so i didnt really care who i was, and put it on random...
ended up getting a cultural victory (imagine that... having at least 150 cities and then FINALLY getting a cultural victory)
now, i find it totally pointless and time consuming to expand that much... so, i expand enough to get everything i need or until room runs out, whichever comes first, then start killing anyone who gets in my way
Most times, I'll rename a captured city, only to tell me that it's a foreign city (say, if i took washington, i'd rename it "Washington (American)" just so i know...
my brother, however always numbers his cities... in the order they were made... "001" anywhere up to "512"
I've yet to SEE him capture any cities, so I don't know if he leaves those alone, or what...