  During its first observing run, in late 2015, the advanced LIGO facility
announced 3 gravitational wave (GW) triggers to electromagnetic follow-up
partners. Two of these have since been confirmed as being of astrophysical
origin: both are binary black hole mergers at ~500 Mpc; the other trigger was
later found not to be astrophysical. In this paper we report on the Swift
follow up observations of the second and third triggers, including details of
21 X-ray sources detected; none of which can be associated with the GW event.
We also consider the challenges that the next GW observing run will bring as
the sensitivity and hence typical distance of GW events will increase. We
discuss how to effectively use galaxy catalogues to prioritise areas for follow
up, especially in the presence of distance estimates from the GW data. We also
consider two galaxy catalogues and suggest that the high completeness at larger
distances of the 2MASS Photometric Redshift Catalogue (2MPZ) makes it very well
suited to optimise Swift follow-up observations.
