#*    *    *    *    *      command to be executed
#-    -    -    -    -
#|    |    |    |    |
#|    |    |    |    +----- day of week (0 - 6) (Sunday=0)
#|    |    |    +---------- month (1 - 12)
#|    |    +--------------- day of month (1 - 31)
#|    +-------------------- hour (0 - 23)
#+------------------------- min (0 - 59)

Examples:

To run every minute:

* * * * * /path/to/my/script.sh

To run every x minutes:

*/10 * * * * /path/to/my/script.sh # every 10 minutes

To run every x hours:

# 5 hours and 0 minutes
0 */5 * * * /path/to/my/script.sh 

# 6 hours and 10 minutes :
10 */6 * * * /path/to/my/script.sh 

To run at midnight :

0 0 * * * /path/to/my/script.sh