Bowie's original intro is pretty simple, but very nice on 12-string.

|--3-----2--3--2--3--2--3-----0--------------0--------------0-----------
|--3-----3-----3-----3--3-----3--------3-----3--------3-----1-----0-----
|--4-----2-----2-----2--2-----0--------0-----0--------0-----2-----0-----
|--5-----0-----------0--0-----2--------2-----0--------0-----2-----0-----
|--x--------------------------3--------------2--------------0-----------
|--3--------------------------------------------------------------------
            H     H  *

* = hold an extra half-beat
H = hammer on from second to third fret


Transition
----------
The transition between C and D during 'the Spiders from Mars' and
subsequent verses goes something like this:

   C                                D
|------------------------------------
|------------------------------------
|------------------------------------
|-----2-----2-----0-----2------------
|-----3-----3-----2-----3-----4------
|------------------------------------
      the   Spi   ders...


Chorus
------
Repeat 3 times:

   A             G               F             G
|--5-5-5-5-5-----3-3-3-3-3-------1-1-1-1-1-1-1-3---
|--5-5-5-5-5-----3-3-3-3-3-------1-1-1-1-1-1-1-3---
|--6-6-6-6-6-----4-4-4-4-4-------2-2-2-2-2-2-2-4---   
|--7-7-7-7-7-----5-5-5-5-5-------3-3-3-3-3-3-3-5---      
|--7-7-7-7-7-----5-5-5-5-5-------3-3-3-3-3-3-3-5---        
|--5-5-5-5-5-----3-3-3-3-3-------1-0-1-0-1-0-1-3--- 
           

then:

   D                      E             
|--5---x-5---x-5----------7---7-7-7-7-7-----
|--7---x-7---x-7----------9---9-9-9-9-9-----
|--7---x-7---x-7----------9---9-9-9-9-9-----   
|--7---x-7---x-7----------9---9-9-9-9-9-----      
|--5---x-5---x-5----------7---7-7-7-7-7-----        
|--5---x-5---x-5----------7---7-7-7-7-7-----  
   *     *     **         *           **

* = hold an extra half-beat
** = hold until the end of the next measure

This is one suggested pattern, but it varies, so improvise.
(My personal preference is to play the D and E in open position.)
On the acoustic and live versions, Bowie and Ronson continue
strumming on the D and E chords.  Bowie also sometimes noodles
around with his pinky on the B string on the D and E chords.
On electric, emphasize the lower (thicker) strings, especially
to get the right sound during the F chord.  The acoustic version
tends to emphasize the upper (thinner) strings.  


Lyrics and chords
-----------------

(Intro x 4, or Intro x 2 in acoustic version)

G                     Bm C
Ziggy played guitar...

(trans) D
G Em
A A7 C
G Bm C
(trans) D
G Em
A A7 C

A  G            F G
So where were...
A G F G
A G F G
D E

(Intro x 2)


G                      Bm C
Ziggy played for time...
(trans) D
G Em
A A7 C

A      G     F G
Making love...
A G F G
A G F G
D E

(Intro x 3) then:

|--3-----2--3--2--3--2--------0--------------------------------3-----
|--3-----3--3--3--3--3--3-----3--------------------------------3-----
|--0-----2-----------2--2-----0--------------------------------0-----
|--0-----0-----------0--0-----2--------------------------------0-----
|--x--------------------------3--------------------------------x-----
|--3-----------------------------------------------------------3-----
				    Ziggy played...