So as not to derail Suntiger's thread, I'm starting a new one here. On that thread, JenniNZ  and Star already explained their systems; other tracking systems can be found (or rigged up) via various apps or in spreadsheet format, and different forum members have done that. Here's a thread from Staysfit about her experience tracking.

I've done the simple Notes feature on my computer (analogous to paper and pencil, and I've also tracked via the FINDS feature on this site. Most of my wardrobe is in Finds, and the last time I tracked I just put a little mark in tne notes area of Finds each time I wore an item. It took a little longer but it was really interesting to see the visuals along with the check marks! I kept it up for a winter season. I've done longer tracking periods -- one year, half a year -- in the past. It's always instructive somehow or other! And it usually prompts me to create new outfits from my own closet. 

Like Bonnie, I quickly learned that I can spend more on footwear and trousers because I wear them a lot. However, unlike her, I find they wear out faster for me than tops do, on the whole. Keep in mind, I do not live in a very hot climate, which I'm sure would affect this. Also, I have relatively more tops than bottoms so rotate through them more slowly. 

I was really surprised last time I tracked with how many wears a pair of indoor shoes got! It was shocking! I had hesitated over buying them because I thought, oh well, what does it matter, really -- but I found I preferred wearing the indoor shoe to my clogs (which function for me like slippers) and I quickly got up to 90 wears in one season!