Fact Fluency for Addition and Subtraction 

Reinforcing Strategies
The link below contains strategies you should use to reinforce strategy development to help with fact fluency.  Research shows only 30% of the population are rote memorizers.  Therefore, memorizing your facts is an ineffective strategy to improve fact fluency. 
Once students have a strategy in place,  you can implement flash cards and/or timed tests.  However, you should only assess knowledge of facts in which students have mastered a strategy.
Games to Build Fact Fluency
Assessing Fact Fluency
Articles About Fact Fluency
Fact fluency video: