Guys- What is the best way for a woman to let you know she is interested without being overly blatant...

Well you can you compliments that aren't too strong, like saying the following below

1 btw you are kinda cool (with a smile)
2 you seem like a very decent person (once more with a nice smile)
3 you know, I know this really nice single girl

come up with something soft and direct. :)

The best way is to find the guy in a social event (party, vacation, etc.) and pay extra special attention to him. Just talk with him more than a casual conversationalist would. ask about what they're studying, or what the feel like doing the rest of their life.

Some guys are thick, and you will have to lay it on pretty thick,

However, some guys speak "girl", and can pick up on most anything that you lay down.

But in order to not leave yourself completely vulnerable (being blatant) your best bet is to approach this person, spend time with them, all in a social type of situation.

Ball is in play.