I show all the fact families with the sum of 8, organized into a table. Seeing the structure and the patterns in this manner helps develop number sense and helps children in the memorization work, also.
Then we drill the facts for a bit. The lesson also includes an exercise of finding missing numbers (a little bit of algebra in disguise), and some word problems.
Addition & Subtraction Fact Families — free online practice here at MathMammoth.com
Addition and subtraction facts with 7 — video lesson
Math Mammoth Grade 1 curriculum