i agreed that try to induce him with his favourite toys, food, colours! ask him to speak out eventhough just one word!
eg: he likes apple, don't give him until he speak out!
i used my son's Cat doll, to play role model, i asked Cat doll to speak out food name, then fed the Cat doll, and then i asked my son do the same, it works! he did the same and spoke out!
Secondly, if you started off with two langauages, like english and cantonese together! then he will speaks late! but he understand both!
my case is my husband and my helper speak in English all the time, i responsible for chinese, he understands both and do whatever we tell him to do, but speak slowly, sometimes he speaks in both languages in one sentence!
my frd's husband is spanish, so three languages at home! his son was born in Oct 09, also speaks less, but understands three languages!
for future is excellent, but for interview K1 is not a good thing!because he has to tone himself and think then speak!
coz, a lot of interview are in Cantonese, unless some!
anyhow, try your best, i m just express my little experience!