Kathy, take a deep breath and relax (I would have a bite of chocolate too, but that's me).
So first question is do you pre wash and dry your fabric first? I find that this helps in a couple of ways - 1st it allows for any shrinkage or color running to take place (shrinkage is ALWAYS different with different bolts of fabric, even in the same lines - it's the fabric NOT us) - because you talk about ironing out wrinkles - if fabric hasn't been washed and you have stubborn wrinkles you can distort the shape of your fabric. 2nd this will allow you to use Best Press, Stay Flo, etc... (everyone has some kind fabric sizing that they like, so this is the time to use it). I always us something when pressing before I cut small or narrow strips (because if they are long strips, you can get some distortion or waves going). If you are strip piecing you also want to sew each strip in the other direction (ie: strip 1 & 2 sew down, then add strip 3 but turn and sew in the opposite direction), this too will help keep 'The Wave' away. Now when you press your seams you can press to one side or open, but no heavy ironing is needed so again 'The Wave' will stay away.
This is what has helped me, so I hope it helps. Good luck