Want to get all your selected tracks lined up at the starting line? This will ensure a clean start to your composition and avoid any flash frames .
Select any layers you want to align. You can Shift+Click to select a range of layers, or Cmd+Click (Ctrl+Click) to select noncontiguous layers.
To align your layers to the start of the Comp, press Option+HOME (Alt+Home).
Alternately, this trick can work to line things up at the end of the comp as well. Just substitute Option+End (Alt+End) to align all layers to the rear of the comp.