Sorry to sound awkward old chap, but there's no standard answer. What country you want to practice in?, what class of aircraft (Part 25, part 23, smaller?) and whether it's fixed or rotary are all fairly pertinent to anybody's ability to give you a meaningful answer.
It's not a straightforward issue of going and getting a particular license as it is with, say, an ATPL I'm afraid. Give us a few clues (also where you're starting from, in terms of age / background / technical and flying qualifications), and I and hopefully others will gladly steer you in the right direction.
G