Building up observational and recall skills ?..advice on how to

In terms of acquiring the skills of recall and observation what advice do serving members have to improve this ?

​

Reading a number of biographies and recollection of training drills , exercises regarding recall and observation seem to be quite common. e.g what was the last street we passed, the second to last car we saw was what color, what was it's number plate etc.

​

Also what other similar exercises have you had to do ?

​

Any tips or advice on building and developing these skills ?