[symestreem]

Gandalf did befriend the hobbits quite early on. He helped them through the Long Winter that occurred when Helm was besieged. Who knows what small local situations he defused or turned to the good of the goood guys? He was probably influencing all the small communities on his travels. Also, the wizards were not allowed to use force, but had to use counsel. This requirement seems to have been relaxed a little for Gandalf when he became Gandalf the White (remember Theoden, and the light on the Pelennor Fields that made the Nazgul leave?)
He probably knew the other heirs of Isildur, since they were fostered at Rivendell, but he did not meet Aragorn until 2956. Also, the story of the dwarf-wars and Gandalf's meeting with Thorin Oakenshield provides some illumination into what he was doing. Was that chance? It seems that Gandalf was just watching out for all of Middle-earth.