One of the keys to keeping the clues from being too obvious is a bit a misdirection. I used to do magic during my younger days. My boss' fiance would hang out at the radio station where I worked at the time. I was supposed to amuse her I guess while he was dawdling over something. I would show her tricks, and she was so easy to fool. As long as I held her eyes I could march a line of elephants through the room and she wouldn't have noticed. So, I would do something big, but unimportant with one hand and then move something into place with the other, often in plain view if she had been looking that way.
You can do the same with clues in a story. Hide your clue like a leaf in a forest. Keep people looking at the trees and not the leaves. For instance, a cookie plays a role in one of my stories. However, it's just introduced by someone sitting around a table having coffee. They are offered a cookie and take it right in the middle of a discussion about the major suspects in the case. The cookie looks just like stage setting. Something not very important, just a sweet with coffee while discussing the important stuff.
Always make a big deal out of the unimportant stuff and be dismissive of the important clues.