We all know the five senses, right? Sight, hearing, taste, smell, and touch. Your characters experience these five senses, whether you describe them or not. The better you do at utilizing all the senses, the more alive your milieu will seem.
But there's one sense that, in my opinion, shouldn't be overlooked. That sense is memory.
Take a look at these examples from Harry Potter if you want to see what I mean.
|Sorry for these crappy photos, by the way. I couldn't figure out how to integrate my Power Point.|
Do you know what I think is the most important phrase in that entire paragraph? "...that Ron had mentioned;"
With four words, JK Rowling makes it clear that Honeydukes existed before Harry arrived there, and that it will therefore continue after he leaves. It's not just a set that Harry wandered through, it's a real place, full of fat toffees and peppermint creams shaped like toads.
If you can find a way to invoke all five of the sensory senses in your descriptions, great. If you can find a way to weave in a sense of memory, even better.