I started with Ray Jardine's Beyond Backpacking and got my wife's sewing machine out of the closet. I had never sewed before. I used 1.9 ounce nylon and 2 layers of fiberfill. I ended up with a slightly too small quilt that weighed 1 pound 4 ounces. I still have this quilt and usually loan it to my son, or other hiking companion if they like the idea. Since then I have made 3 more quilts. I have some advice and improvements. In the first place, it is worth it to find 1.1 ounce nylon. If I were to make another quilt, I would buy a Ray Jardine kit. His price is very reasonable compared to buying materials retail at fabric stores. Plus you get Jardine's pattern. This will give you much better odds that the quilt will fit you!
In use I found that I was usually chilly due to drafts under my quilt. My solution, which I have not seen anywhere else, was to sew a single layer of nylon under the quilt. This basically turns the quilt into a sleeping bag. It adds very little weight but much warmth. I do not put in a zipper. I simply wriggle into the bag and do not find it to be inconvenient. Since I never get too hot in these bags, I don't need a zipper for temperature control.
It is good to sleep warm at night but not carry too much weight of course. I find that a quilt with 2 layers of fiberfil is adequate for July and August hiking in the Washington Cascades. But for early and late hiking I take a warmer bag with 3 layers of insulation. This will keep me very comfy to about zero degrees.
I take a few other cold-night precautions. For an exceptionally cold night I will put on a vapor barrier. This is simply a kitchen size garbage bag that I wear as an undershirt. Yes, it is uncomfortable. But it adds considerable warmth, weighs little, and keeps moisture out of my bag. Lightweight women's tights keep the legs warm.
I have also slept in bivy sacks over my bag and found them to add much warmth. But this is heavier than the vapor barrier.