Pull the bottom blade up instead of pushing the top blade down. This is just the opposite of the motion you are familiar to using when cutting with scissors. Keep the top blade aligned over the metal sheet and bring the bottom blade upwards, cutting from the bottom side up.
Purchase the correct set of tin snips. The colored handles aren't just for decoration, the red ones are for left-handed cutting and the green ones are for right-handed cutting. That doesn't mean you should only buy green ones if you are right-handed, because there will be situations where you will need to cut with left-handed tin snips.
Use green-handled tin snips if you are cutting a curve that runs clockwise and use red-handled tin snips for a counter-clockwise curve. This allows the rise of the cut piece of metal to extend over the top blade, allowing you a smooth path to cut.
Wear leather gloves when you cut sheet metal. A soft flexible pair is a good choice. Sheet metal edges are very sharp and will cut through flesh easily. A long-sleeved shirt will protect arms.
- Try pulling the tin upwards as you cut. As you cut with green-handled tin snips, pull the right side up as you go. Do the same with the left side and red-handled snips.