[geeper]

Here is a grid our Spanish instructor drew for us that helped me a lot.

Position of object    | El    | La      | Los      | Las      | Unknown |
_________________________________________________________________________
Near you              | Este  | Esta    | Estos    | Estas    | Esto    |
Near person spoken to | Ese   | Esa     | Esos     | Esas     | Eso     |
Not near either       | Aquel | Aquella | Aquellos | Aquellas | Aquello |

Its kind of hard to make this out but if you find the type of object across the top (el,la,etc) then look down the left column and determine where the object is you can find what to use. e.g. La object near the person spoken to, then you use Esa. Hope this helps.