If you are having a problem like the one I had where labels were centered in my vertical stack panel, make sure you use full width controls. Delete the Width property, or put your button in a full-width container that allows internal alignment. WPF is all about using containers to control the layout.
<StackPanel Orientation="Vertical">
<TextBlock>Left</TextBlock>
<DockPanel>
<Button HorizontalAlignment="Right">Right</Button>
</DockPanel>
</StackPanel>
Vertical StackPanel with Left Label followed by Right Button
I hope this helps.