1. What do the following words have in common?

END
RISE
LAUD
ROVE

2. What do the following words have in common?

HOST
MISS
TEXT

Answers:

1. Each of the words can be preceded by APP to make a new word:

APPEND
APPRISE
APPLAUD
APPROVE

2. Each of the words can be followed by ILE to make a new word:

HOSTILE
MISSILE
TEXTILE 

Credit:
#2: Paula Gamache