Mac question about deleting files?

Okay, so I hope this is simple. Somehow on my Macbook, I switched some setting somewhere: I used to be able to add files to the trash bin, in order to store files before I actually delete them. Now when I hit command-d, it asks for my password and deletes the said files immediately. Same if I drag it into the trash “bin.” This isn’t ideal, as if I have a number of files I want to delete, I like to “look” at them before I make the final judgement call! Help! Oh, and it’s Mac OS 10.8.2 with all the updates…