My little one has just started saying more words, but he still doesn't specificy exactly what he wants to eat. So I generally run through a list of things till he says "yeth" (yes), but these days does he just seems to say yes to everything, 2 months ago it was No to everything.
At 16 months we used to let him go to the fridge or pantry and point out what he wanted.

I think 16 months is a little young to be expecting too many words, only recently have I been able to point at things in a book and has he been able to say 'shoes, socks, pants' etc... I think the best way to go about it, as the ladies have said it lots of repetition. I point at pictures in books and say 'Whats that?' If he knows it, he will try to say it and then I will say 'Well done' and repeat the word. If he doesnt know it, I say the word a couple of times.

You will get there, there is just a tough period where they have opinions/needs but can't express them, and you're in that now!