1. What do the following words have in common?

POSITION
SELECTS
IMPEDE
BESTS
PANS
DOT

2. What do the following words have in common?

NO
UP
CAP
HER
CART

3. What do the following words have in common?

WALTZ
HAND
RICE

HINTS:
1. It has to do with synonyms of each word.
2. It has to do with adding letters to each word.

Answers:

1. The synonyms or near-synonyms of these words are anagrams of each other: 

Position - POST
Selects   - OPTS
Impede - STOP
Bests    - TOPS
Pans    -  POTS
Dot      -  SPOT 

2. Each word can be changed into a new one by adding the letters ON.

NOON / UPON / CAPON / HERON / CARTON

3. Each word can be preceded by MINUTE.