Hint: Double letters
The answer to this puzzle is:
1. BALL
2. CELL
3. ROOM
4. SOON
5. ASSET
6. BEECH
7. MOODY
8. ANNEX
9. GEE
10. SAVVY
11. DUMMY
12. PUPPY
2. CELL
3. ROOM
4. SOON
5. ASSET
6. BEECH
7. MOODY
8. ANNEX
9. GEE
10. SAVVY
11. DUMMY
12. PUPPY