Advanced LIGO and Virgo are poised to detect gravitational waves (GW) directly for the first time this decade.
The ultimate prize would be joint observation of a compact binary merger in both gravitational and
electromagnetic channels. However, GW sky locations uncertain by hundreds of square degrees will pose a
challenge. I will explain how we will promptly detect GW sources and rapidly estimate their parameters and sky
locations within minutes. Having analyzed a comprehensive population of simulated GW sources, we describe the
sky localization accuracy that will be achieved in the first two years of Advanced LIGO. Next, in preparation
for the optical search with the intermediate Palomar Transient Factory (iPTF), we are following up gamma-ray
bursts (GRBs) detected by the Fermi Gamma-ray Burst Monitor. Its comparable error regions offer a close
parallel to the Advanced LIGO problem, but Fermi's unique access to MeV--GeV photons and its nearly all-sky
coverage may allow us to look at optical afterglows in a relatively unexplored part of GRB parameter space. We
present the discovery of iPTF13bxl, the optical afterglow of GRB 130702A. Recovered from a targeted survey of
71 square degrees, it is the first optical afterglow found based solely on a gamma-ray localization. It is
also remarkably nearby (z=0.145), and its supernova fills in a gap in the GRB--supernova connection. We also
present iPTF13dsw, the optical afterglow of GRB 131011A, recovered from a similarly sized region but much
fainter and further away (z=1.874). iPTF13bxl and iPTF13dsw point toward more afterglow discoveries with iPTF
and Fermi. Furthermore, they set the stage for finding LIGO optical counterparts with the Zwicky Transient
Facility.