"He's a threat, he's a talent, but one thing I would say is that when he's not scoring he needs to mix his game up a little bit," he told ITV.
Rashford made an impressive appearance for England in their World Cup qualifying match against Lithuania on Sunday, but Giggs feels that the 19-year old has more to offer.
"More one-twos, laying it off, because at the moment he's getting the ball and taking players on, but you can't do that every time," the Welshman said.
"Sometimes you have to keep the defender guessing, just control pass, lay it off, and then next time run at him, just constantly cat and mouse.
"Keep the defender guessing, because he has got everything, he can run in behind with or without the ball."
Rashford is yet to find his scoring form under Red Devils boss Jose Mourinho. The promising youngster has made 22 Premier League appearances this season, but has notched up only three goals and one assist.