The time to go to Ducky's is not on a weekend. In fact, it's way too busy on a weekend. When you're wanting karaoke and you need a bit more of an updated song selection than Nanta's, Ducky's can be your stage on a weekday night... like a Wednesday for instance which is where I found myself after hitting up Model Milk.
Karaoke starts right around 930. Don't get there too early. Because, really, there's not a whole heck of a lot of reasons to head to Ducky's early anyway... unless it's to peruse the one karaoke book that's already set out and get your songs in early.
The song selection is vast, and you'll get the odd awesome old person there to serenade the women in the crowd with lovely oldies (gentlemen, take note. I don't know a girl out there who doesn't melt when a man is singing her an old school love song. Any man... grab that mic and work your charms).
That's the thing about Ducky's... it's not so dive-y that it scares me to go, but enough so that everyone kinda fits in.