Experiences are the name of the Game
Experiences: Having many objects pass by the infantís eyes, ears and hands, gives them the opportunity to recognize (learn) objects. This is exercising the memory tracts and making neurons expand like popcorn.
We are talking toys here. Not just an amorphous array of plastic objects, but objects of many textures, (cloths, wood, plastic, paper etc.) and many shapes (balls, squares, rectangles, polygons, dolls, imitation fruits and vegetables, etc.) and sizes!
This requires considerable monitoring on the part of the caretakers. Objects have to be selectively placed within the infant's (toddler's) reach, and the infant (toddler) must be monitored at all times for safety's sake.
Games: Playing little games with the infant, like patty-cake and many others (available in many baby type books) is an excellent way to start. Later on most games that have parts and procedures will stimulate the memory tracts.