It had promised to be a nervy night for the visitors, who had lost all four of their pre-season games and who had a clutch of players missing for various reasons.
However, Neil Lennon’s side, especially in the first 45 minutes, showed the professionalism and purpose which had taken them to the last 16 of the tournament last season, including a thrilling victory over Barcelona in Glasgow.
Full-back Lustig gave the Scottish champions the lead at Solitude in the 25th minute when he broke away from the Reds defence at the near post to head in a Kris Commons corner.
Six minutes later Greek forward Samaras, who had revealed his aversion for the ground’s artificial pitch before the game, finished off a move involving Forrest and Commons by turning at the edge of the box and driving an unstoppable shot past Reds keeper Conor Devlin.
And in a one-sided first-half, watched by almost 5,000 enthusiastic fans who had packed into the tiny ground in north Belfast, Commons also hit the woodwork twice.
With nothing to lose, Tommy Breslin’s side rallied in the second half, with Stephen Garrett missing a good chance in the 48th minute from close range after Lustig was short with a headed back pass.
Anthony Stokes hit the bar for Celtic with a drive before he set up Forrest in the 84th minute to hammer the ball low past Devlin from inside the box to make the return game in Glasgow a formality.
CLIFTONVILLE: Devlin, McGovern, Caldwell (Martin Donnelly 73), Marc Smyth, Ronan Scannell, Johnston, Gormley (O’Carroll 69), Garrett (Curran 78), McMullan, Catney, Boyce.
CELTIC: Forster, Lustig, Wilson, Ambrose, Izaguirre, Forrest (McGeouch 86), Kayal, Brown, Commons (Rogic 81), Stokes, Samaras (Watt 76).
Referee: Sergiy Boiko (Ukraine).