Where to go first
The Moon is a big place, and we can only work a small area first. The current thinking is Shackleton crater, but, either prove us wrong, or help us with our argument. Tell us exactly where to land first. Please be as specific as you can.
12/30/08 Given the difficulty of just reaching the Moon, we need to locate on the surface area most easily reached from the chosen launch site. Shackleton is out. A 90-degree plane change pre-landing is going to have ruinous payload penalties. Shackleton can be reached overland after the initial (transportation) base is operable. Though probably not until after we have gone through chinese customs.
(NOTE: the idea that a 90 degree plane change is needed to get to Shackleton is based on a misunderstanding of orbital dynamics. There is no significant difference between approaching the Moon from Earth over its equator, at 45 or -45 latitude or over a pole - that approach latitude is what determines lunar orbit orientation. You just enter the inclination you need, without any need to change.)
You need to start by establishing a lattitude for the launch site.
As a baseline, launching north of 28.5 degrees north (or south) of the equator can be ruled out as not real favorable form a payload perspective.
On the lunar surface, an equatorial base makes a balance from between a transportation point of view for launch frequency and payload performance. Starting with the zero-degree meridian, I would not station more than 85 degrees east or west. This ensures your communications will always be line-of-site and not through any kind of relay.
You want to avoid mountains too close to the landing site.
Ideally, you want to be near a point where the maria makes contact with a mountain range for best availability of useful minerals.
This suggests five sites: @64-degrees west, northwest of crater Lohrmann A; 30-degrees west, directly west of crater Lansberg; 0/0-degrees, smack in the middle of Sinus Meridiani (Sinus Medii! Meridiani is on Mars); 24 degrees east, just to the north of crater Moltke (and east of Rima Hypatia, south of the Apollo 11 site); 58-degrees east, northwest of crater Webb.
Of course, this is not an exhaustive analysis. In any case we really should be emphasizing transportation requirements for Base #1.
Some different thoughts about sites: Shackleton, or similar polar sites, are favored because of prolonged illumination and possible volatile resources. The equatorial zone lacks those attributes, but another type of site favored for resource potential is pyroclastic deposits. Examples of those close to the equator include the Rima Bode area and a dark mantle south of Copernicus (both considered for Apollo, Bode considered for Constellation). Neither is close to highland terrain as such, for access to additional raw materials, but both, especially Bode, are close to patches of Fra Mauro Formation (Imbrium ejecta).
One question to consider: do you land from and return to orbit, as Apollo did? If so, the poles and any point on the equator are overflown on every orbit by orbiting assets (comsat, return spacecraft, orbital station...). But a point at any mid-latitude location is not because of the rotation of the Moon under the orbit plane. That limits emergency departure opportunities. This was the reason why early Apollos (and the Soviet lunar cosmonaut plans) required landing very close to the equator. Later Apollos were designed so the CSM could change orbit planes as necessary to accomodate a few days of lunar rotation. Constellation will do that too. If you land and depart directly you don't have that limitation.