Click the link above to view a tutorial.
This is best for shirts that are a tunic cut, or even using this method to take a dress into a shirt. This will also work in transforming a shirt into a crop top.
(These are not formal hemming instructions, this is a very casual cut that will leave a raw edge.)
First, try on the garment to get a feel of where you wish to cut. Mark the shirt in some way such as with pen, or a snip, or if you're not very accurate a pencil.
Second, lay it flat on a smooth surface (carpets work too) and prepare your scissors!
Lastly, decide which type of cut to make. In the film, I make a rounded hem cut. This leave the sides shorter than the front and back. You can also make a straight cut.
And you're done! Put the shirt back on and see if it needs any extra snipping. :)
Sorry the photos are not of great quality. I didn't take formal before and after photos, but next time I will!