On land maps, City placement depends on whether or not you're going to be aggressive. I've learned that just placing your 2nd City and 3rd City as far forward to your enemy will avail any needed Timber spots and Mountains. If you're going to be defensive, place your 2nd and 3rd Cities near the Timber and Mountain spots, but still in the direction of your enemy if possible. This ensures quick garrisoning of your Citizens, and you don't have to spend too much resources on Tower protection.