1. What do the following words have in common?

OF
FIT
PER
DUCT

2. What do the following pairs of words have in common?

COME - STOP
EARLY - LIVING
SLOW - EAT
WIN - FIND

HINTS:
1.VERB could be added to the list.
2. LEFT - WRONG could be added to the list.

Answer:

1. Each word can be preceded by PRO:

PROOF
PROFIT
PROPER
PRODUCT
(PROVERB) 

2. Each pair of words shares a common antonym:

COME & GO
STOP & GO

EARLY & LATE
LIVING & LATE

SLOW & FAST
EAT & FAST

WIN & LOSE
FIND & LOSE 

(LEFT & RIGHT
WRONG & RIGHT)