To me thats the one of the fun parts, and will admit sometimes it dosen't go well :), Brain seems to go into overload with all the prettys to be seen, have found that pick a few, combo together, can do with more than one combo at a time, then walk away, look at something else. come back and glance to see what hits you as right. do it as many times as needed, (when it gets to the point your tearing the store apart, clerk will be very helpful :) )
But sometimes it just dosen't feel right, or is not the right day, Good Luck you'll get it worked out