First was Hagrid taking Harry from where the Dursleys tried to hide him, stopping by his vault at Gringotts, shopping at Diagon Alley then taking him to Kings Cross Station where he left him to "stick to your ticket." Molly Weasley showed him how to get onto Platform 9 3/4.
Second year was Ron and Harry flying using Ron's dad's Ford Anglia because Dobby had magically blocked access to the Platform, attempting to prevent Harry from going back.
Third was Hogwarts Express. He had left Privet Drive on the Knight Bus after he had blown up Marge, his Uncle Vernon's sister. So the Weasleys took him from the Leaky Cauldron. There was a nasty incident with a dementor on the train.
Fourth was Hogwarts Express. But first, Harry went with the Weasleys to see the Quidditch World Cup.
Fifth was Hogwarts Express leaving with the Weasleys and Order of the Phoenix protection from Number 12, Grimmauld Place. M.O.M. Fudge almost got him expelled that summer after he fought off dementors with a patronus charm. He had to be cleared of charges at a hearing on August 12th.
Sixth he got to the Weasley's house, the Burrow, by Dumbledore and then from there he took the Hogwarts Express with Order of the Phoenix protection.
Finally, in seventh book he didn't return to Hogwarts until May 1st. The coup at the Ministry took place on August 1 as Bill and Fleur's wedding reception was in progress. They disapparated to hide and begin the search for horcruxes. On May 1st, they returned to Hogwarts to head off Voldemort and find th Ravenclaw horcrux that Voldemort had hidden there. They disapparated into Hogsmeade village where they were nearly caught, saved by Aberforth Dumbledore and returned through a tunnel from the Hog's Head to the Room of Requirement led by Neville.