The steps:

1. From the Mac OS X Desktop, open any new Finder window
2. Hit Command+F to bring up Search
3. Click on “Kind” filter and select “Other”, then select “File Size” from the attribute list
4. Click on the second filter and choose “is greater than”
5. In the third space, enter the size to search for anything greater than (ex: 100) and choose either MB or GB as the final filter

Original source