After you have taught "M" I would begin on S. That is another fun one and you can use sssssnakes to help teach them how to make it. I forgot to mention when you are trying to help remember the M you can teach mountains. They have a good m begining and an "M" looks like a mountain. Likewise a S looks like a snake, which is what it starts with.
The next letter would be "B". That is another fun one and you can incorporate bubbles into that one. It kind of looks like a couple of bubbles yeah? After "B" we will begin working in some sight words the kids will need to know for reading simple books.
At this point they should be able to read mmmmm about something that looks good to eat. They should be able to say the "sss" sound when they see "s" in a book. The best thing for you to do is read to them. When you are reading let them make the begining sounds they know up to this point. If you are lucky they are starting to put things together and see how this letter thing works.
The problem we are having right now is with learning to read in English and Spanish at the same time. They are a little later to teach reading here in CR, but baby is learning her vowels at her school and keeps getting them confused with English vowels. I just have to keep reminding her, yes that is in Spanish, but we are learning to read in English right now. She is getting it, just a little slower than she would if everyone around here was speaking English.