I will sometimes use fabrics from the same collection. However, if I find a fabric that I love and want to use, I just go throught the LQS with the fabric in hand and try on different fabrics. When I pick my fabrics this way, I rarely go with "matching" but more of a "Go with" mentality. I look at different colors and values and sometimes a fabric that is standing by itself and not a color/print/pattern I would normally pick will actually look wonderful with my focus fabric. I go with colors that compliment and enhance each other. I've always had a flair for colors and picking the right colors to go together and that just spilled over into my quilting.