it comes down to your judgement/decision in a lot of cases.
i also avoid buffets and times when the food has beensitting for along time. freshly cooked and piping hot is the main thing and also avoiding known listeriosis risks like soft cheese, smokes fish and cold cuts, raw fish (sushi).
Personally I also avoid caffeine (tea and coffee) as much as possible also taking into acct the caffeine in soft drinks and chocolate (hard to avoid this totally LOL)