Required work experience between 2 and 5 years minimum, must be gained within the last 10 years.
At least one year of this experience must be recent, and gained on an airplane of the licence you are asking for.
Recent experience means :at least 6 month of the last 12 month. The rest may be gained within the last 7 years. 

Military, police etc.: 1 year experience in a civil maintenance environment appropriate to the category applied for.

EASA part 66 How To Get on site!

Regulation EU1321-2014 - The How To

Your way to get the licence: You study the modules at home, take exams at a part 147 school or a National Authority like the CAA. While you are studying you start filling out your work experience logbook . When you have completed all 13 or 14 modules you apply on EASA form 19 for the licence.