When I'm making a scrappy type of quilt or one with various types of blocks, I'll arrange them on my design wall and leave them there so everytime I walk by I can stop, look at the arrangement and make some changes if I deem feesible. Then leave the new arrangement there, walk by from time to time making changes as I see fit. Finally when I know I've walked by a number of times and haven't made any changes, then I know I've got it the way I like. Also taking a photo of it and viewing it on your PC seems to help me to see problems especially if I stitched the block wrong so I can fix it then and not after its all been put together. There's nothing worse than finding a mistake after its all put together or you have it on the quilt frame stitching away. Sometimes I'll ask my sister's view on it as I know she has a good eye for color.