At first when I started cardmaking several years ago, I would find a design that I really liked I would try to find the same materials used so I could replicate it exactly. This often left me frustrated. Then I realized that it probably wasn't what the designer had in mind in the first place. Like, "Oh maybe this is just to inspire me to do my own!" Sometimes I admit I'm not very bright.
Anyway, now I will pull a pattern that I like, such as this one:
I'll look at the supplies they used (i.e., 2 kinds of cardstock, 3 patterned papers, 2 accents, etc.) and just rummage through my stuff until I find something I like. In this example my card isn't identical, but it is fairly similar. Sometimes there is no resemblance whatsoever. I guess it just depends on my mood and what I have on hand.
This has honestly cut the time it takes for me to make a card in half. If you are a cardmaker, try a recipe every now and then! My favorite sources are Cardmaker and Paper Crafts Magazines, as well as scrapbook page designs. I've heard some people even use advertisements or catalogs, but I've tried niether.