We also get the "nothing" and the "don't remember". When our DS was that age, he really needed time to decompress from the day before he wanted to talk at all. Sometimes it would start in the car later in the afternoon on the way to practice, but often he was most open to talking at bedtime (delay tactics, anyone?). There is something about cuddling in the dark after lights out that made it easier for him to just start gabbing.
This will probably not be helpful if your DS is having any language issues (sorry, can't remember specifics) but this year our DS has to write a weekly letter about his school week (assignment from school). It has been fantastic to really hear details and how he feels about things- turns out he remembers and can relate things in excruciating detail, which is really surprising to us. And he writes pages and pages- it's fantastic, and already has me thinking about journals for what this assignment is over, just to keep him writing. We write back each week as well, and it has turned into a great form of communication for us.
