1. What do the following words have in common?

CUT
GOB
HAM
TAB

2. What do the following letter pairs have in common?

AY
EY
OT
OY

HINTS:
1. The same three-letter word will change each word into a new one.
2. The same three-letter word will change each letter pair into a word.

Answers:

1. Each word can be followed by LET to form a new word:

CUTLET
GOBLET
HAMLET
TABLET

2. Each letter pair can be preceded by ALL to form a word:

ALLAY
ALLEY
ALLOT
ALLOY 

Credit
#2: NY Times Crossword
Matt Gaffney
AFTER ALL