what you need:
- an old tshirt you don't mind cutting
- put on your shirt and decide where you want to cut and mark it
- this way you don't "go in blind" and don't end up cutting too much
- take the shirt off and complete the lines
- take your scissors and cut! simple as that
- pull the fabric a little so the seam starts rolling in and you can't see where you cut anymore
- done! takes about 10 minutes?!
- little tip: when cutting off the sleeves, cut straight down and then out, so you get kind off a right angle, otherwise the sides are going to look like weird wings.