I don't use this often so I end up googling it every time I need it.
mysqldump -u root -p database_name > sql_dump_file
Now I know exactly where to find it and I don't have to scan a whole article just to get the syntax.
Change "root" to the user you normally use; you an also specify
-ppassword (no space between
-p and the password) so you don't have to enter the password interactively ... security issues etc but if you're running this from a script I'm not sure what the alternative is.