Decluttering is something that often come with difficulty to a frugal person. We tend to want to hold on to everything because we might find a use for it.
However, remember that holding onto something, unused, until it's unusable is not thrift. It's waste. So, if you have a coat that you really know you'll never wear again because it doesn't fit or you hate the color or it's too out of fashion, find it a home. You might be able to sell it, but unless you really can expect to make some money out of it, it's probably faster and less hassle to donate it. Plan regular days to do some decluttering, whether it's a once or twice a year big cleaning, or one evening a month to clean out a closet or cabinet.
Any clothes you haven't worn in a year probably should go. The exceptions might be specialized items like maternity clothes that you expect to wear again and possibly something you particularly love that's JUST half a size too small. I actually have about half a dozen suit jackets in a storage tub because I don't need them for work right now. But eventually I probably will, and at the least, they'll keep me going while I slowly replace them (avoiding the major expense of buying an entire new wardrobe at once).
Any small appliances that you haven't used in 6 months probably can go as well. A lot depends on the item. A small hand mixer might be worth holding onto if you use it once a year for a lot of holiday baking. A special hand drink mixer that you can only use to make a few drinks that you don't even like that much is probably a dust collector. The same with pots and pans.
And make sure to clean out the pantry too. Check for expiration dates, even on your staples, and use the oldest items first. Any time there's a food drive, check for foods that are close to their date, and give away the ones you know you won't use in time. For me, this is the "feel good" side of my bulk buying. If I overestimate, it will go to feed someone worse off than I am, while still staying within my budget. And I rather like donating food since I know what it will be used for.
Be realistic. Yes, you probably loved that copy of Masters of Orion I. But you haven't had a 3 1/2 floppy drive in 6 years and even if you did, it would never run on your current system. VHS tapes. Rolls of film that are way past their expiration, for cameras you no longer own. Cameras that you no longer use because you have and use a digital. Fabric that's been waiting over 10 years for you to turn into that lovely quilt (find it a home before it dry rots). Yarn you meant to use for learning to knit, in a color that you'll never use with anything in your home.
Remember, it isn't thrift if it goes to waste.