Know when to call a pro vs. DIY
A single trash bag is a DIY job; a garage full of furniture, a busted treadmill and old paint cans is not. If an item is too heavy to carry safely, won't fit in your car, or the local transfer station won't accept it, a full-service junk removal crew saves you the rental truck, the dump run, the fees and a sore back.
The tipping point is usually volume and effort: once you're looking at more than a car-load, or anything that takes two people to lift, hiring out is almost always cheaper than a weekend of your own time plus disposal costs.