Priority ranges in Linux varies from -20 (greater priority) to 19 (lesser priority). So, the lesser the value, the greater is the scheduling priority.
Use nice is simple. In the example shown bellow, we want to run the program "your_program_name" using priority value 10:
nice -n 10 your_program_name
The default priority value is 0. If you want to set a priority less than 0 (greater priority than the default), you should run it as system root.