The other day, my son was looking for a ball. I pointed to it and said "it's over there." I had never thought about it, but "over there" doesn't give you much information. It tells you that it's not close to the person talking, but that's about it. There is very little language development/learning happening. When kids are little, they need EVERY opportunity they can get in order to learn language. Therefore, I'm getting on my soap box and shouting from the top of my lungs (or keyboard): NO MORE "OVER THERE".
Instead of saying something is "over there", tell your son or daughter that his/her shoes are "under the couch" or "behind the shelf" or "next to the chair" or "near their bed". Those descriptions may be simple, but they are teaching your child different prepositions. Your child will learn that "under" means that it is below something simply by hearing "under" and then you helping your child find the object "under" the couch. Same thing for all the prepositions.
The same thing goes for "I'm right here." How much does that really tell us? Not much. Instead say something like, "I'm in the kitchen in front of the stove." Give as much detail as possible to give you child as much language as possible. If you have an older child, then teach him/her to also be descriptive. That will help with his/her expressive language and other littles ones in the house will have another person teaching them prepositions!!!
Also, let's not forget about those who are working on listening comprehension. This can easily be turned into a great game. Pick out a little toy (i.e. a rubber duck, doll, block, etc) and put it somewhere in a large room. Have the child ask "where is the ____" and respond with a descriptive answer (not "over there") like, "on the table." The child will be rewarded with he/she sees the toy. Then have him/her tell you where he/she found it, "I found it on the table." What a great prepositions game!!!