A couple of weeks ago I noticed a creaking noise coming from the left side of my drive train, so I did what I normally do - I ignored it. And it went away. And then it came back. The noise appeared to come from the area where the left crank arm attaches to the spindle and progressively got worse. So I tried spitting water on the crankarm as I pedaled along and that seemed to make it happy. I figured there must have been some dust or sweat-crud lodged in a crease somewhere. However, the noise kept returning. It was then that I noticed that the left crankbolt had come loose and upon tightening it down the noise went away. Several times the creaking resumed and I found that I was having to tighten the crankbolt every 15 miles or so. (Luckily the crankarm also has "pinch bolts" that hold it on as well.) Finally the noise became constant whether the crankbolt was loose or not and I began to suspect it was going to be rooted in the bottom bracket.
As I rode along muttering profanities and dreading the impending trip to the bike mechanic I thought of one last "user friendly" repair (if you count ignoring and spitting water as actual "repairs") that I could try. I removed the spindle cap from the pedal body, applied a couple of drops of chain lube and Viola! No more noise.
So, what I thought was going to be an expensive bottom bracket repair actually ended up being a creaky pedal and it helped me discover a potentially dangerous situation involving the crankbolt. A torque wrench should solve that problem.