I was just wondering what the symptons of an "unstraight" fretboard is, when the Truss Rod needs to be tightened, just to make sure that mine needs adjusting before I take it to the tech.
The big thing that will tell you if it's not straight is if it's not straight...

Get a long ruler and place it on the fretboard, makes it easier to tell if it's bowed.
fret the first and last frets. check the distance from the top of the 7th or 8th fret and the strings. there should be enough space. for a perfectly straight neck, i guess there should be a very very small space.
Ibanez RG321MH (Air Classic/Tone Zone)
Fernandes Telecaster (Twang King/stock bridge pickup)
Blackstar HT-20 (Scumback 55 speaker/ Tung Sol tubes)
TC Electronic Nova Repeater
Lava Cables Clear Connect, Soar and Mini ELC
aye, you can use a feeler guage to measure the gap in the strings when they fretted like the dude above me said...
also, one of those metal steel-rules are handy aswell...
they're not 100% perfect, but they're pretty damn good...