You can start by making a pile of stuff you want to sell on eBay. I've sold for over 10 years and find that I get better than garage sale prices without the hassle of standing outside waiting for people to paw through my stuff, only to get a quarter for a great pair of shoes.
You have to be organized too, take all your photos of items at once, get your packing boxes and weigh the items in shipping boxes so you can put the right amounts in the auction selling templates.
Then one by one, make the listing as honestly as possible. Make sure to disclose all the flaws, as well as the good things about "recycling" that particular item.
Watch the money flow in (it won't be millions), but one man's junk is another man's treasure!
You will be glad you started selling your junk on eBay!