When Richard visits young John Locke, he asks him to identify the items that belong to him, even though he never saw them before. This is the same way that the fourteenth Dalai Lama was found; monks showed him several items, of which he positively identified several that had belonged to the previous Dalai Lama by saying they were his. This convinced most Buddhists that he was the reincarnation of the former Dalai Lama, and therefore their rightful spiritual leader.
When Richard visits John as a small boy and "tests" him, Richard sets a comic book on the table among the items for John to choose from. The comic book is a reference to the island with the caption "Mysterious Land" on the front.
When Richard comes to visit John, he is playing backgammon. This is the same game that John taught Walt to play and is shown randomly throughout the series. When Locke first teaches Walt to play the game, he explains that it is a game of "dark and light, good and evil." This is another reference to what happens with the constant struggles on the island between the Others, the 815 survivors, and the people on the ship.
Mittelos, the summer camp that John's teacher tells him to look into, is the same name as the company that recruited Juliet in Lost: Not in Portland (2007). Mittelos is an anagram for "Lost Time" or "Lost Item."
The trivia items below may give away important plot points.
Although John Locke (Terry O'Quinn) says he is not like Ben (Michael Emerson), they have more in common than he knows. Both their biological mothers are called Emily. Both men survived despite being born very premature, had no relationship with their natural mother and a problematic one with their fathers. They both recovered on the island from a condition that crippled them (albeit Ben just temporarily). And both of them end up being chosen by the island to lead the inhabitants.
When the young John is looking at the items on the table, he chooses the bottle of sand (possibly from the island?) as well as the compass. We later find out that this is the same compass that Richard himself gives to Locke in the 50's during Season 5.