Here is a picture of ZoarZoar in her "living room." I made a few of the miniatures myself and found the rest around the house. You can save a lot of money by making your own miniatures or "shopping in your house" for items you already have. This post will focus on things I bought or already had. Next time I'll talk about making minatures. So.... read here and then start looking around your house for things you can use!
You can use math and the scale of the dolls. Your 18 inch doll reprenents a 8-11 year old girl. The average height for girls is 50-57 inches. Let's use 54 inches as the height of the girls. This is in the middle of the range and divides by 18. So, a 54 inch girl is 3 times the height of an 18 inch doll. This means your minature should be 1/3 the height and 1/3 the width of the real life object. You don't have to use fractions of inches. Real objects vary a lot, so round to the nearest half inch and you'll be okay.
If you have objects that aren't quite the right size, try them out. They will work if they are close. After a while you will get really good at judging.
ZoarZoar's sofa is a sewing pin cushion/thread storage miniature that I got on sale at a sewing notions store a friend of mine owns. I didn't measure it at the store, but thought it was about the right size for a small love seat or bench. It looks a little short here because ZoarZoar is standing on a doll stand that adds about one inch to her height. It looks better when she isn't in her stand.
The depth of the real bench seats are 16-17 inches. ZoarZoar's 5.5 inch deep bench is in the range (3 X 5.5 = 16.5). The height of the real bench seats are 18 inches and 21 inches on the cushioned bench. ZoarZoar's 6.5 inch high bench seat is in the range (6.5 X 3 = 19.5). The back on my real benches are 36-37 inches. ZoarZoar's bench is 10.5 inches which is a little small, but still pretty close to the range (3 X 10.5 = 31.5) so it works.
Two of ZoarZoar's baskets (on on the left here) are miniature collectable baskets I bought many years ago. They can be pretty expensive, but if you already have them, they are "free" to use.
Remember that real basket come in all different sizes from the size of a coffee mug to the size of a laundry basket or a hamper, so most mini baskets will work if you use them for the right purpose. As you can see, ZoarZoar's little gold basket is s pin cushion I made years ago and decided to donate to ZoarZoar's room.
Books and magazine: Books can vary a lot from a paperback book (Real magazines aren't all the same size, but most are about 8 inches wide and between 10 and 10.5 inches high. These numbers don't divide nicely by 3, so just get close. Use 2.5 inches for the width and 3 or 3.5 inches for the height. The book of about 3.75 by 7 inches to a big "coffee table" type book 9.5 by 11 inches to 11 by 14 inches. This means that the miniature quilting book 3 by 3.5 inches would be real book of 9 by 10.5 inches and fits into the coffee table book size.
The quilt on ZoarZoar's bench is a miniature quilt I made with tiny scraps from a little quilt. I didn't make it for ZoarZoar at the time, just for fun. This is one of the things I found when "shopping around my house" looking for things for ZoarZoar's living room. It is 5.25 by 7 inches so it's a little quilt for ZoarZoar that she might use as a wall hanging or as a doll quilt.
The quilt on ZoarZoar's wall is a little quilt I made a long time ago. It is 17.5 wide by 21 inches tall and might be just the size quilt ZoarZoar would make for a nice lap quilt so I hung it in "her room." The denim wall hanging was made for ZoarZoar's room from scraps I had made testing my needle felting machine. I put them together to look like a fiber art wall hanging ZoarZoar could have made.
The biggest secret to making a miniature room look real is to avoid oversized (real size) objects being too close. Look how you can tell ZoarZoar's room is tiny when you see the real furniture in my sewing room.