Well... depends... how fast are you trying to lower the population and how drastically?
If you are not going for a major drop in the population and are willing to wait for a long time, I'd start tampering with public views and access to things like abortion and fertility treatments and the like.
(Note: I am not stating my personal views on either of these.)
More people than you would think have to use some sort of 'extra measure' if they want to have children, nowadays. I am counting in this things like medications, paying extreme attention to 'cycles', adoption, surrogate mothers and so on. To lower population, make these less accessible and turn public opinion against them.
With abortion, the reverse, try to get the population to see it in a more favorable light, and make it more accessible.
It wouldn't be all that obvious (if at all noticeable) that anyone is trying to affect population levels through this, and due to these being... controversial... topics, it would only take pushing the right 'buttons' to create a massive change in public opinion (and embarrasingly few people seem to have 'inbetween' opinions on these, it's mostly all-or-nothing).