The Dutchman, who guided the Netherlands to the World Cup semi-finals, landed at Manchester airport at around midday on Wednesday and travelled to United's Carrington training complex in the afternoon.
He then met with chief executive Ed Woodward and coach Ryan Giggs, along with the United players, and oversaw a period of a pre-season training session.
Van Gaal will take training in earnest on Thursday before holding his first press conference in the afternoon. He has already spoken about building a strong bond within the squad, with reports suggesting the players will be told to eat together at Carrington every day.
United fans will be hoping for an immediate impact from the 62-year-old, after last season finished not only trophyless but without Champions League football for the first time in 18 years.
But Rene Meulensteen, a former United coach under Sir Alex Ferguson, insists his fellow Dutchman will relish this challenge.
"I don't think it will faze Louis van Gaal at all in that respect, there are no worries there," he told Sky Sports News. "He will only thrive on it to some extent.
"But you really notice it when you're really getting into the routine, especially when you're going into pre-season and you see the massive popularity of the club and brand, that's what it is.
"To maintain that they have to get back up very, very quickly."
Van Gaal has acquired a fiery reputation during his hugely successful managerial career and Meulensteen believes the players must accept it or face a swift exit from the club.
"He's got his own management style, which has thrown up a few difficulties along the way wherever he's been, Barcelona or Bayern Munich because of the way that he is, the way he puts himself in front of players," he said.
"Players accept it or players sometimes don't. If they don't accept it, then yeah you probably have a problem."
A seventh-place finish in the top tier underlined how far the club have slipped behind their main rivals and there is only a month before the opening home fixture against Swansea.
Meulensteen, who worked alongside Sir Alex Ferguson, admits van Gaal will need time to build the club back into one of the major forces in English football.
"They've had Sir Alex Ferguson and they've had a disastrous season with David Moyes, now another one comes in, so that will take time," he said.
"United at this moment in time, (will be) seen by the opposition still a team that can be beaten unless proven otherwise."
You can watch Van Gaal's first press conference as United manager from 3pm on Sky Sports News on Thursday.
@lfcfan80, well, both were bad ideas, let's be honest. Probably arranged by the kind of people who laugh at their own jokes, wear novelty socks and still believe it's funny to make a sarcastic comment and finish it with "........NOT!".- HarryBoulton