One of Yoda's objections to training Luke is that Luke was too old. Obi-Wan was well aware of the age issue for training Jedi, but was ready to train Luke when Luke was somewhere around 20, much older than when Anakin started his training at about 9 years old. There had been no apparent attempt to train Luke until he intercepted Leia's message for Obi-Wan via Artoo.
In other words, even with an awareness of the need to train a Jedi at a young age, and after seeing the problems with Anakin, whom the Jedi Council didn't want to train because of his age, Obi-Wan waits until an emergency leads to Luke coming to Obi-Wan before he makes any apparent attempt to train Luke.
Obi-Wan didn't take any apparent action until Luke came to him.
We know, as was brought up in this question about Obi-Wan trying to train Luke when Luke was young, that Obi-Wan encountered resistance from Owen Lars. It's also been brought up, in another question that we really don't know Obi-Wan's original intent.
But considering Owen Lars' resistance and the need to train Jedi at a young age, are there any indications that Obi-Wan was not only watching Luke from a distance, but was finding ways to subtly prepare him for Jedi training? Perhaps he was using the Force to influence Luke or to increases Luke's sensitivity?