Basics

find . -type f # find files not directories
find . -type d # find directories not files
find . -name "victim*" -exec rm -rf {} \; # execute rm -rf X on matching files and directories -- note the \; needed at the end
find . -max_depth 1 ... # only search the current directory
find . -max_depth 3 ... # only search 3 directories deep
find . -name "*.zip" -ctime -1 # find .zip files created today (useful in Downloads)
find . -name "*.zip" -size -1M # find .zip files less than 1MB in size.

Some useful examples

Find files ending in either .mp4 or .mkv or .mov (ignoring case)

find . -type f \( -iname "*.mov" -o -iname "*.mkv" -o -iname "*.mp4" \)