Song: Ambulance Blues
Artist: Neil Young
Album: On The Beach
Tabbed by: Kris Pender
Tune down 1 whole step (D G C F A D)

Plectrum is of no use for this song. Neil plays it in a kind of freestyle clawhammer way:
downstrokes are hit with the edge of the thumb, upstroke hit with middle or ring finger
(held in shape of a 'claw'). The tab's not perfect, but the structure is fairly 
accurate, and it should be a good start. 

Downstrokes are marked ^

Intro:
   ^       ^       ^       ^       ^       ^       ^       ^
d|---------------------0---0-----|-0h3---------3-------3-------3--|
A|-1-------1---1-h-3-------1-----|-1-------1---1-------1---1---1--|
F|-0-------0---------------0-----|-0-------0---0-------0---0---0--|
C|-2-------2---------------2-----|-2-------2---------------2------|
G|-3-------3---------------------|-3-------3---------------3------|
D|-------------------------------|--------------------------------|
                  C                               C/G

  ^       ^       ^       ^       ^       ^       ^       ^
|-3-------3---3---3---1---1-----|-1---1---1---0---0---0---0---0--|
|-1-------1---1---1---1---1-----|-1---1---1---1---1---1---1---1--|
|-2-------2---2---2---2---2-----|-2---2---2---2---2---2---2---2--|
|-3-------3-------3-------3-----|-3-------3-------3-------3------|
|-------------------------------|--------------------------------|
|-------------------------------|--------------------------------|
         F/G             F                        Fmaj7

  ^       ^       ^       ^        ^       ^       ^       ^
|-0-------0---0---0-------0---0--|-0-------0---0---0-------0---0--|
|-1-------1---1---0h1-----1---0--|-0-------0---0---0h3-----3---0--|
|-2-------2---2---2-------2---2--|-0-------0---0---0-------0---0--|
|-2-------2-------2-------2---2--|-2-------2-------2-------2------|
|-0-------0-------0-------0------|-2-------2-------2-------2------|
|--------------------------------|--------------------------------|
                  Am                           Em(7)

  ^       ^       ^       ^        ^       ^       ^       ^
|-2-----------2-------0-------2--|-----2-------0------------------|
|-3-------3---3---3---3---3---3--|-3---3---3---3---3---3---3---3--|
|-2-------2---2---2---2---2---2--|-2---2---2---2---2---2---2---2--|
|-0-------0-------0---0---0---0--|-0---0---0---0---0---0---0---0--|
|--------------------------------|--------------------------------|
|--------------------------------|--------------------------------|
                  D                              D

Verse
  ^       ^       ^       ^       ^       ^       ^       ^
|---------------------0---0-----|-0h3---------3-------3-------3--|
|-1-------1---1-h-3-------1-----|-1-------1---1---1---1---1---1--|
|-0-------0---------------0-----|-0-------0---0---0---0---0---0--|
|-2-------2---------------2-----|-2-------2-------2-------2------|
|-3-------3---------------------|-3-------3-------3-------3------|
|-------------------------------|--------------------------------|
                  C                               C/G

  ^       ^       ^       ^       ^       ^       ^       ^
|-3-------3---3---3---1---1-----|-1---1---1---0---0---0---0---0--|
|-1-------1---1---1---1---1-----|-1---1---1---1---1---1---1---1--|
|-2-------2---2---2---2---2-----|-2---2---2---2---2---2---2---2--|
|-3-------3-------3-------3-----|-3-------3-------3-------3------|
|-------------------------------|--------------------------------|
|-------------------------------|--------------------------------|

  ^       ^       ^       ^        ^       ^       ^       ^
|-0-------0---0---0---0---0---0--|-0-------0---0---0---0---0---0--|
|-1-------1---1---1---1---1---1--|-0-------0---0---0---0---0---0--|
|-2-------2---2---2---2---2---2--|-0-------0---0---0---0---0---0--|
|-2-------2-------2-------2------|-2-------2-------2-------2------|
|-0-------0-------0-------0------|-2-------2-------2-------2------|
|--------------------------------|-----------------0-------0------|

  ^       ^       ^       ^       ^       ^       ^       ^
|-2-------2---2---2---2---------|-2---2---2---2-----------2---0---|
|-3-------3---3---3---3---------|-3---3---3---3-----------3---0---|
|-2-------2---2---2---2---------|-2---2---2---2-----------2---0---|
|-0-------0-------0-------------|-0-------0---------------0-------|
|-------------------------------|---------------------------------|
|-------------------------0h2---|-----------------0h2-------------|

Play this with variations throughout (e.g., Em to Em7, D to Dsus2, Am to Asus2 or Asus4, etc.)

Other parts of song have straightforward picking pattern:

(G)
Oh, Isabella, proud Isabella,
(Am)
They tore you down and ploughed you under
(Bm)                       (C)
You're only real with your make-up on
(G)                 (D)
 How could I see you and stay too long