A great activity for your dog is “search-fetch”. When you go out with the dog just drop something from yourself next to your path. Take care that the dog is not walking the same way then you and is not noticing what you are doing. Continue the walk, depending on how well you dog is trained on it. Call the dog to you and let him sit. Point on your track and say the command. The dog should follow exactly your track (not his own) and bring you what you dropped.
The advantage of this activity is, that it is a really nice nose work and can be done always and everywhere.
It is important to not make it too difficult. Always make it so easy that the dog has success. The dog learns the best when it works, not when it is challenging. How you teach commands in general will be covered by another post.
This is a very useful command if you loose something.