# To find files by cas insensitive extension (ex: .jpg, .JPG, .jpG):
find . -iname "*.jpg"

# To find directories:
find . -type d

# To find files:
find . -type f

# To find files by octal permission:
find . -type f -perm 777

# To find files with setuid bit set:
find . -xdev \( -perm -4000 \) -type f -print0 | xargs -0 ls -l

# To find files with extension '.txt' and remove them:
find ./path/ -name '*.txt' -exec rm '{}' \;

# To find files with extension '.txt' and look for a string into them:
find ./path/ -name '*.txt' | xargs grep 'string'

# To find files with size bigger than 5 Mb and sort them by size:
find ./ -size +5M -type f -print0 | xargs -0 ls -Ssh