1. Know what you’re looking for!
2. Start big.
3. Look at areas that are more contrasty.
For example, patches that have lots of height variant, edges of patches near sidewalks or anything not green, etc. so that it's easier on your eyes in all the clutter.
4. Once you find one, get closer!
Rake through the patch and it's neighboring areas with your hands, where it's little mutant brothers and sisters should be hiding.
5. Shamrock mutations aren’t necessarily restricted to only four leaves!
6. Be patient!
Not all patches have the mutation, so you're not always guaranteed to find one. If you find yourself getting impatient or frustrated, leave the patch and continue your search elsewhere.