We spend $23.5bn on foreign assistance, much of which is mismanaged and corrupted, and not ending up in the hands of those to whom it's intended (i.e. the poor!). The next president needs to make a concerted effort to reform our broken foreign assistance programs. We should use PROVEN models of assistance that will provide for wealth accumulation for the poor from the bottom up -- things like development of microfinance, conditional cash transfer programs, and child development accounts.
On Day One, the next president should call for a summit meeting in Washington for all great powers - including allies, Security Council permanent members like China and Russia, and emerging powers like India. Rather than enlarge the out-of-date UN Security Council, the next administration should convene this "global great power concert" with informal meetings of heads of state on a regular basis.
Recommit to the Anti-Ballistic Missile (ABM) Treaty. In order to have a serious discussion with nations like Iran and North Korea about limiting nuclear technology and weapons, we need to lead by example.