for me I dont't really have a systematic way of introducing the alphabets & numbers. I believe more in exposure and exploration for my daughter's current age. i teach her as and whenever i can.
it may take some trial & error before you realize what type of learning is suitable for your child.
we read books on a daily basis so it exposes her to words. occasionally i will bring out the flash cards to show her words like, "daddy, mummy, milk, etc" which are words that are already familiar to her, so she picks them up faster.
recently I've also introduced the numbers 1 - 10 but that is more of a lot of repetition. these can be in many forms, newspapers, flyers, magazines, counting her blocks, counting her fingers, etc. so far she can catch 1-3 and 6.
she will usually catch the sound of the word first, then once she is familiar with it, i will introduce her the word. So if she recognizes RED, when I show her the word she will pick it up faster.
so far she has not learnt to talk, & it takes time for me to realize that she recognize certain words and numbers.