Always works fine for me, as CynicalAftermath said... Make sure you copy the whole script.
Click 'Use in-Game'
Ctrl+A -> Ctrl+C
Go into game and open chat
Ctrl+V
Hit Enter
For example, Random Retribution Paladin spec : http://www.wowhead.com/talent#sbhMZMZfbGsdkszfz
Code:
/run t,p,a={3,12,23,32,53,62,71,83,92,101,111,121,131,143,161,172,183,201,1,12,33,62,2,22,}SetPreviewPrimaryTalentTree(t[1],GetActiveTalentGroup())for i=1,#t do a=t[i]if a<9 then p=a else AddPreviewTalentPoints(p,floor(a/10),a%10)end end
If all else fails, just make the screen half 'n half and click them in. :P