I have had this problem also. I do look for ones that are not "too" transparent, usually with a white on white print. Washing/drying first definitely helps and once you sandwich it with white batting, it comes out beautifully. Once the piecing is done it helps to make sure there isn't any darker fabric peaking out from under the white on that occasion when you have to press to the light side, if it does, it doesn't hurt to trim a little off so it stays behind the white. You will also want to make sure your darker threads are clipped from the back so they don't show through.
When you wash the completed quilt for the first time, don't be alarmed when you see the darker colors through the white while wet (ask me how I know), once dry it'll be just fine!