1. What do the following word have in common?

WIT
CRY
FEAT
RING
PANT

2. What do the following words have in common?

ME
FED
MIRE
HERE
DRESS

HINTS:
1. The same three letters will change each word into a new one.
2. The same two letters will change each word into a new one.

Answers:

1. The letters HER can either precede, follow, or be inserted into each word to form a new one:

WITHER
CHERRY
FEATHER
HERRING
PANTHER

2. The letters AD can either precede or be inserted into each word to form a new one:

MADE
FADED
ADMIRE
ADHERE
ADDRESS

Credit: Both puzzles: LA Times Crossword
Sylvia Bursztyn and Barry Tunick

Puzzle 1: THE LADY VANISHES
Puzzle 2: NON-COMMERCIAL