Hi there! Are you using a commercial pattern? I have found that that pattern companies will print the information on their pattern right side up. So if you lay your pattern so that you can read the pattern piece correctly, then the top of the pattern will be true top. Another way to confirm this is that one side will have more curves than the other. A small curve at the top will be the neckline. The large curve is the armhole and therefore the side of the pattern and the side that may be completely flat is the hemline or the bottom of the shirt. Hope this helps!