If you don't have a spoke wrench yet, get one. Park makes an inexpensive multi-size one. A pair of needle nose pliers will work better than nothing. Your LBS may have the Park spoke wrench.

I had a strange clicking noise emanating from what I thought was the front hub of my mountain bike several months ago.
Checked the front hub (just repacked a couple of months before). It seemed fine.
Totally repacked the headset. Still had the noise.
Thought about my 15 year old Phil BB and thought it could be that. Nope. Still like butter.
Concluded that the noise was produced under heavy load (pulling a trail-a-bike).
The culprit was a couple of loose rear spokes that tightened up in about 30 secs. with the help of the spoke wrench.
And to think I had all kinds of expensive solutions floating around in my head and it was as simple as this .