Since you already know your child is speech delayed, we assume that he's working with a therapist on a regular basis. But there's a lot you can do to support your therapist's efforts at home. First, think about some of the things your child enjoys. Music is a great way to teach new words, for example. Sing songs about body parts (like "Head, Shoulders, Knees, and Toes") and point out the parts whenever you have a chance, such as while getting dressed or taking a bath. "Wheels on the Bus" is another great song for learning about objects, so sing the song and point out all the wheels you see when you're outside as well as all the doors and windows (that go open and shut). Or if your son loves to snuggle up with a book, choose titles that highlight everyday objects and activities, and use the words as often as possible. Let your son stop in the middle of the story to talk about it as often as he likes.
It's also important to chat with your son as much as possible about your daily routine, from cooking dinner to laundry to grocery shopping. You may start to feel a little crazy (or get some odd looks at the supermarket), but trust us, it will pay off. Describe your son's activities as well. For example if he's petting the family cat and says "kiy, kiy," answer with something like, "yes, that's our kitty." This way he will hear the correct word being used. As you talk, always encourage your son to mimic you. Rest assured that just because your son's speech is delayed, it doesn't mean he will always have language issues. The majority of speech issues are resolved by school age.