Any area where shoppers may take a break or congregate is good. Try to get a major entrance. People are more inclined to be interested when they first step into a mall, particularly on the weekends. I recommend doing this only on weekends. Weekdays attract a demographic that is a tough sell.
Folks tend to want to get in and out on the weekdays and often have no time to dally.
Shopping malls typically will provide both the table and chairs, usually accommodating two to four persons. This way they are fresh and enthusiastic about talking to the people. Try to have a single activist who will stay all day and coordinate the shift changes. Ideally, this person should be an officer of the local party affiliate, preferably the chair or vice chair. This lends authority to the activism and allows the public to know our officers are concerned enough to conduct outreach in person.