Suetonius says that Caesar and Octavius met on one occasion, during Caesar's Spanish campaign. Octavius was supposed to meet Caesar at several points, but always something got in the way. Octavius was going to join Caesar early in his Spanish campaign, but his chronic poor health prevented him from leaving until quite late, when the campaign was all but won. Octavius, in his haste to join Caesar, had his ship wrecked and was washed up on the shore, where he proceeded to hike through enemy territory to reach Caesar's camp. Suetonius says that Caesar was impressed by Octavius' determination, with the assumption being that since this coincided with Antony's falling out of Caesar's favor this favorable impression influenced Caesar's decision to change his will and make Octavius his heir. There's not really any reason to doubt it, but only Suetonius, of our main sources, provides this story and it reads suspiciously like something Augustus might have said in later life to legitimize his claim. A few very late sources expand on the story, saying that Caesar let Octavius ride in his carriage with him after he reached the camp, but we have no real reason to think that their testimony is accurate, given how late they are. But we don't really have any good reason to doubt Suetonius, even if it seems too good to be true. Now, this is the only recorded meeting between them. There may well have been other, secret meetings, the way that we only have a single meeting between Caesar, Crassus, and Pompey, although they were undoubtedly together on other occasions as well (such as at Luca).