1) Massive social support for child-rearing to essentially bride people to procreate.
2) Liberal immigration policies geared towards increasing the working age population and filling in skill gaps.
3) Already being a society that is primarily oriented towards religious orthodoxy.
We've seen many nations try #1, sometimes in ways that are extraordinarily extravagant (especially by US standards of social welfare) and the results have been mild at best, if not entirely insufficient.
We've seen nations such as the US and the UK go for #2 with amazing results. And although that may not be sustainable forever it is certainly sustainable for a few more generations at the very least based on global birth rate trends.
Personally, I want nothing to do with #3 and would never want to live in such a society. I imagine large majorities in developed nations generally agree.
Option #2 still seems like the best bet.