THE FIGURE
I started with the "Buck" Apollo Astronaut figure from Dragon Models.  They have done a fine job of representing the look of the real thing, but there is always more you can do...

CUSTOMIZING
I looked at several actual photos to decide how I wanted my figure to look.  Since it will not be any particular astronaut, I can be creative.  Many of the photos and diagrams I found useful can by seen here.  To see an artist's rendition of the Apollo suit, click here.
I scratch-built the microphones and added an antenna to the OPS (photo #2).  I painted the hose connectors that attach to the suit, and kit-bashed one to look like the purge valve with the "red apple", then I made my own waist belt, buckle, and snaps (#3).  I added controls to the chest pack and ran a hose from there to the OPS (#4).  I added the red stripes to the suit showing this is a mission commander.
I took the pictures in front of a flat black background and added a cut-out of the earth.

GETTING CREATIVE
The three photos below were done by combining photos of my customized figure with actual moon landing photos using a computer graphics program.