My favorite Christmas song by far. For the Am6 it goes like this

Am6--1-- (x02212@1)--1--
--2--
--2--
--0--
You don't have to play it you can just skipit and go staight into the D at the beggining 
"Christmas".

G (320003@1)               Am (x02210@1) (Am6) DI'm (xx0232@1)dreaming of a white Christmas
C (x32010@1)           D (xx0232@1)           G (320003@1)  D7Just (xx0212@1)like the ones I used to know
          G (320003@1)       C9Where (x3233x@1)the tree-tops glisten
    C (x32010@1)      CmAnd (x3101x@1)children listen
   G (320003@1)  C9 (x3233x@1)   G (320003@1)          D7 (xx0212@1)   DTo (xx0232@1)hear sleigh-bells in the snow

G (320003@1)               Am (x02210@1)  (Am6) DI'm (xx0232@1)dreaming of a white Christmas
C (x32010@1)        D (xx0232@1)              G (320003@1)  D7With (xx0212@1)every Christmas card I write
         G (320003@1)     C9 (x3233x@1)  C (x32010@1) CmMay (x3101x@1)your days be merry and bright
        G (320003@1)      C (x32010@1)     D (xx0232@1)    GAnd (320003@1)may all your Christmases be white

And thats it, you can keep repeating it as many times as you like I find it best to 
a D7 at the end for a turnaround if I'm going to continue. Merry Christmas