First, try not to worry too much. My sons have both had speech delay, one has Asd, the other doesn't.
The youngest is 2 y 4 m and has only just started to say a few words.
We did baby signing, which was ignored by DS1 (the one with asd) and is used by DS2 to great effect. He even makes his own signs up!
We just keep talking.
Offering choices
Giving him a chance to speak
Eg
..."What do you want for breakfast?" Pause
Him: hmmm
Me: cornflakes? Shreddies?
Him: hmmm
Me: cornflakes?
Him: shakes head
Me: shreddies
Him: big smile, " aah"
With DS1 he couldn't have indicated too well verbally so we had lots of laminated little pictures of usual food, drink choices, books, dvds, places we visit etc and would show him a selection from which to choose.
If you have an ipad or iphone there are some great apps for making little symbols and pictures for choices.
The key is encouraging communication, showing them it's worth the effort, that they get a reward when they make the effort ie something they want.
Other tips, read stories, lots of them. Leave a pause sometimes for them to 'fill in the missing word' even if they just grunt say " that's right!" Lots of praise.
My eldest said 'mama' for the first time at 2 and 1/2 and is now one the most articulate 5 year olds you could meet