Answer:
1. quiero (1st person singular)
2. prefieres (2nd person singular)
3. prefiero (1st person singular)
4. cierran (referring to las tiendas, which is a 3rd person plural)
5. pienso (1st person singular)
6. empiezan (referring to las ofertas, which is a 3rd person plural)
Just keep in mind the patterns!
Yo form = -o
Tú form = -s
Ustedes form = -n