The best approach is to first program in every language, Google the various jobs available since most tech companies dislike the traditional model of organising businesses there is always a difference in job titles etc. But you will need to be good in Maths, English and Physics at O level. Do an A level combination which somehow includes Maths it does not matter at this level if you do Physics or not but it would be useful sometimes although depending on what you later decided to do Commercials might be a better fit.
If your question is how I would start to program: you need a Software Development Kit for the Language that you choose. I would recommend starting with Python, its a simple high level language which even if the programming gig does not pan out, you will find useful in your own little projects. Php is another language. You might also find it useful to learn to use a Linux OS. Ubuntu is a good start. Hope that settles it.
Also you might want a college/university qualification that majors in programming. My advice if you are serious with your life stay away from the UZ's useless courses but that' just me, do your own research. If you have money you might want to visit SA's better equipped Universities.