Having worked on doubles in the past couple of weeks, we are now trying to use that knowledge to help us develop quick tricks for solving other problems mentally.
The idea of 'Double Plus One' is that your child should recognise a sum that is almost a doubles problem. So if (s)he knows that 6+6=12, when they see 7+6, they should think:
"Well I know that 6+6=12, so I just need to add one more on to that to get 7+6. 7+6 must be 13."
Use this approach to learn all of the tables this week.