You cannot. Not with current technologies. If you were to develop space travel- sure, why not colonize other planets? That leaves you with Taxation- something Australia is soon to embrace.
China has been using abortion and infanticide to keep it's growth slow, and it has not worked as well as the UN had hoped.
A lot of people like to talk education, but that only goes so far. It sounds good, it sounds productive- but the reality is it does not work beyond a certain reach. More is not better.
If you do not want to kill, and you want to limit population growth- it is an unachievable goal without resorting to social engineering, eugenics and genocide at our current level of technology.
Let us set aside for the moment that there is NO population crisis. There really is no crisis because the starvation and famine have mostly been the results of displaced population displaced by war. It is the distribution of food that is the problem. Heck the whole world's population would fit inside the borders of the US state of Texas.
Taxation is one of the growing trends to slow population growth, but who is going to think about that in the heat of a lust filled interlude? Scientists are already exploring the means of dispensing "vaccines" that sterilize people- That has occurred in Africa via the UN vaccine program a few years ago. While some of this may seem an attractive solution to school aged kids "...eager to contribute to positive change to save the world...." The reality is the rights you surrender by signing onto one of those schemes are your own. It is social engineering taken to the next step- that of Eugenics. because if you are limiting births, whose are you going to allow? What are your criteria? The US has a death cult facet to education, which is reinforced by trash on network television. So the matter of abortion becomes trivialized because of the social engineering that has gone on at all levels.
One thing is for sure- anyone who speaks of controlling population is going to end up resorting to genocide or eugenics. Who is worthy? who is not worthy? It will be sanized by "panels of ethicists." As rational sounding as the proponenets are- if you are not a member of some 20 or so families, or not within the monied sphere of influence- you could be very well signing your own death sentence. Or surrendering your right to have a kid.
Education does not work beyond a certain point.
Taxation does not work beyond a certain point.
Martyrdom is not an option.
So your options are:
Waging war. Against whom?
Selective breeding- allowing only the "beautiful people" procreate.
Culling- eugenics practice to cull out the weak, infirm, disabled, elderly. Think of "Logans Run."
Massive pandemic disease- easy enough to produce something in a well funded lab. Take your pick. A strain of Ebola perhaps? Spanish flu anyone?
Lottery- seems to sell a lot of tickets. Of course you could end up like the movie "The Island"
To implement such a program of controlling population growth, you are embarking upon eugenics and genocide- even if you apply it proportianately to every country of the world. Even if you are trying not kill anyone, you are engaging in social engineering on a grand scale and those promoting it should be suspect. Follow the money. After all, Prince Charles considers all the mineral wealth of Canada for example- to be his. Or Australia, or other "countries" of the former British Commonwealth.