• Cache folders (.DS_Store, sass_cache)
• Modules/Packages folders generated by dependency managers (node_modules, vendor)
• Any folders that can be easily regenrated on the other end by a config file
• Configuration files. Anything that contains private usernames and passwords

Following are common files added to my .gitignore

# Mac OS X
.DS_Store
*/.DS_Store

# Opencart
image/cache
system/cache # OC 1x
system/storage/cache # OC 2x
vqmod/vqcache

# Webhost
cgi-bin

# Dependency and Package folders
node_modules
vendor

# Sass
sass_cache