The freshest ingredients?
Although the wet markets offers the freshest ingredients, but I shop in supermarkets where it is more hygienic.(I'm a guy & Singaporean guys don't always cook)
I always buy from Cold Storage where they call themselves "The Fresh Food People". Although their seafood is not live, however the condition looks good. For the fishes, no bruises, red eyes instead of dull yellowish eyes, bright red gills, shiny scales. Their tiger prawns comes with shiny shells with that blue tint colour, only a few of their prawns comes with the reddish(spoilt) tint in the flesh.
For meat, such as beef, I will always look for those with a reddish colour.I won't want those with a brown tint.As for poultry, no bruises & I will prefer those whiter in colour rather than those with a yellowish colour.
For vegetables, it is the most easiest. Look for the bright colour tone instead of a dull colour. Regardless it is green, purple or red etc. Also look out for worm holes. You won't want vegetables where the worms had the 1st bite.
The most obvious sign a spoilt food regardless of any type, sticky liquid which drips from the surface & it smells really bad. You won't go wrong with the supermarkets. Most of them provides fresh food unless you are down with your luck.
Source(s):
My mother who is a great cook, a gluttony tastebud which made me done lots of trial & errors with different recipes.