1. What do the following words have in common?

AT
MAN
WAN
OGLE
SLING

2. What do the following words have in common?

DO
ID
GO
WE

Answers:

1. The letters (word) GO can precede, follow, or be inserted into each clue to form an new word:

GOAT
MANGO
WAGON
GOOGLE

2. Each clue word can be preceded by the letter A to form a new word:

ADO
AID
AGO
AWE 

Credit #1:
NY Times Crossword
December 31, 2015
Ben Tausig
GOSLING