Ultimately a student should just know that 7 x 8 = 56 without thinking too much about it.
The recital of timestables allows the child to learn the series of numbers but I tend recall a school joke where little Johnny was asked to recite his six times tables, he replied dah, dah, de, dah, dah, dah, de, dah, dah, dah, de, dah, sorry miss I know the tune, but I don't know the words.
I believe that tables should be taught as rote initially, then each table should be randomised so that the students imprint the individual sums in their long term memory and is able to recall them.
When a student gets to the 6 difficult sums I suggest the following activity:
e.g. learning 7 x 6 = 42
Calmly say, seven times six is forty-two, seven times six is forty-two, seven times six is forty-two...................(nine times)
The psychology behind this is that an individual can store 7 items +/- 2 in their short term memory. If the short term memory is "loaded" with nine identical pieces of information then it is likely that a large portion of this information will transfer into long term memory for later recall.
24 hours after the first exercise the student should be tested for recall, if recall is not successful then the exercise should be repeated.
This is a neat little trick that should only take one-two minutes per day for three or four days.