Several different schools of thought exist with regard to where we should target our interstellar travel resources.
The immediate thinking is of course on proximity. With interstellar distances daunting by even theoretical standards, exploring our immediate galactic neighborhood seems the logical choice. Stars within 50 light years
Some consider a more focused approach to our interstellar itinerary prudent. Recent advances in deep space observation aided in part by the Kepler Telescope have begun to identify star systems with planets. Estimates of earth-like planets just in our galaxy range into the 100′s of millions.
Another approach for planning our interstellar voyages centers around the presumption that we wish to find other advanced species. One definition of ‘advanced’ is space-faring. It would be far easier to run into these entities at the figurative watering holes of the universe, tourist destinations, areas of particular scientific interest rather than hope to find specs of life on individual planets circling obscure stars. In our own galaxy these include (but certainly aren’t limited to) star clusters, star clouds, swirling rings of gas, nebula, Supernovae sites, and even a large black hole.
Of course focusing on a specific target or finite range of targets assumes the short-term, existing assumption that travel will be slow (relatively speaking) and that we will have limited resources with which to pursue interstellar exploration. Advances in FTL (superluminal) travel may make these assumptions obsolete. We may be able to go wherever the desire leads us.