Some People are Blessed or Born Actors , it is instinctive Basically as a mother who knows how to raise a baby without any training so basically it is something which interests you . To Become an actor there is no age bar and there is no requirement to take classes as such , it is only if you want to learn professionaly from some established actors some particular techniques in terms of Dialogue delivery , voice modulation, expressions, how to face a camera and have good lighting etc etc.
Acting is like singing the more you Riaz IN SINGING THE MORE YOUR VOICE SHARPENS , and in Acting the More you Practice to shine your skills the more you come up to be a professional actor, in this case you can PRACTICE AT HOME OR join already established institutes or Individual Celebrities for their workshops/Courses which they tend to have or organise most of the times there are Reputed Institutes like National School of Drama where the likes of Manoj Bajpai, Irrfan Khan, Anupam kher , Nazeeruddin shah and many other prominent film personalities have studied and several other institutes /colleges are there which you can find out through various mediums the best happens to be Google also you can ask for references of your known People in your Circle or Preferrably somebody already in the Acting profession can be a Advantage . Acting as they say is a short lived career so you should also develop a backup plan as when you age the scope of work decreases in most of the cases . The confidence matters the most to become an Good Actor and to leave impeccable impression in the hearts of millions of people across the globe weather it is hollywood or Bollywood .