Currently, a new Lazarus project use this directive:
{$mode objfpc}{$H+}
Which works nice with Lazarus, but won't work with Delphi.
Since I write all of my code to be compatible to both (Delphi for historical reasons on Win32, FPC/Lazarus on others), I always have to change this. For full compatibility there, my suggestion would be to use these directives in new file templates instead:
{$IFDEF FPC}
{$mode objfpc}{$H+}
{$ENDIF FPC}