This is a common problem in retail having:
Slow stock does sell but only slowly.
Dead stock does not sell at all.
Both cost money to the retailers, costs cash flow, money and takes up space that should have stock that sells better.
Now in identifying your products that are slow or dead go to register reports > stock titled "Old Stock on hand by Date last received"
I tend to do it in two parts. I check the overall problem in the shop to see the scale of the problem. Then I go by department in detail as its people find it better to examine this way.
This gives you a listing of your stock based on when you received it. This stock is rarely doing you much good. As I stated, it costs you to keep it.
Now once you identified it, what are you going to do about it?
I would suggest firstly move it because maybe it was in the wrong area. Good clean and a nice presentation can do wonder.
If your decision is to minimise your losses on this stock by slashing the price and to move the stock here are some options.
1) Offload them on sites such as eBay.
2) Use it to make a bundle. Put an old stock item that does not sell with something that does sell and turn it into a bundle.
3) Make a bargain bin.
4) Use the stock for your loyalty marketing program.
5) Use them as specials when you have a marketing season.