I also have trouble with matching seams sometimes; I will try some of your suggestions as well.
One thing I have learned when I first started was to square up the blocks using the smallest and most "perfect" block as a guide. Of course the ultimate goal would be having all of the squares the same size that you originally intended. But when you can't; this will help keep all of your squares the same, and so you can match the seams with all the methods suggested here in this blog. THank you all for your suggestions.