You can also get a lot of stretching when you press seams on a stripped piece. Say you have sewn three strips together, alternating the direction of your seams...and then you take it to your ironing board and you lay the whole piece down horizontally...of course so it fits on the ironing board all at once. But you do a dis-service to yourself...because most people really iron...pressing hard and not lifting the iron up & down....so they iron back and forth - back and forth along the seams....And when they pick it up, it looks like a rainbow. Try placing the sewn piece vertically on your ironing board and lifting the iron up and down - up and down - up and down as you "press"...
What a difference this can make in your sewn seams for a newbie. Good luck and never be afraid to ask....you will get a lot of wonderful information on this board!