I am a huge fan of small changes that you can build upon throughout the year. And one of my go-to's is the 1-hour closet cleanse. I do this at least 2x a year.
Next, you'll look through the remaining items in each pile for pieces to donate. Grab things in good condition and that you are okay parting with. This pile of your wardrobe should be items that are good pieces, but they just don't fit in your life anymore. Like the bateau neck sweater that I wear every week last winter, but this winter I barely ever even consider it. Say a quick "thanks" to the pieces and place them in the donate bag/bin.