Watch for spikes in any case (using an ammonia badge), but there are some bacterial products that can give you a head-start. Bio-Spira and Dr. Tim's One-and-Only, from what I've been given to understand, are live ready-to-rumble bacteria. Some of the other products are dormant, and may take a few days to a week or so to really get cranking. Setting up my most recent QT, I used bacterial products - and while I didn't see my ammonia badge change colors, I did notice that the water was unalterably cloudy for the first few weeks, even with water changes. Over the last couple of weeks though, it's cleared up rather nicely.
~Bruce