A general aviation pilot missed the hold short line and sign for Runway 06 at IAG and taxied across without clearance.

Narrative

Having received IFR clearance from Niagara Ground; I was directed to taxi from the FBO ramp to Runway 6 via Taxiway J. I was unfamiliar with the airport; having flown in for the first time two days prior to this event. I wrote the taxi clearance on my kneeboard and had the FAA airport diagram in my lap. I identified the locations of the FBO ramp; Taxiway J and Runway 6 on the airport diagram. All communication and NAV radios and the GPS were set prior to taxi. I was directed to perform my run-up at the hold short line. I exited the ramp and identified a Taxiway 'J' location sign (yellow on black). On the way to that sign; I noted that I was crossing a runway and realized that it was Runway 06. Having already entered the runway; I chose to exit by continuing across. As I did so; I heard ATC (though I was still tuned to the ground frequency) cancel another aircraft's takeoff clearance. That aircraft was departing from Runway 24 (opposite end of same runway; which is 5189 FT long). I was instructed to proceed across Runway 06; turn 180 degrees on Taxiway J and hold short of Runway 06; which I did. I performed my run-up and called Niagara Tower. I was given the Tower's telephone number to call upon reaching my destination; which I did. I believe that this event occurred because I was unfamiliar with the airport and the hold short line was not where I expected it to be. Having reviewed the airport diagram; I expected to taxi onto J at least a short way before coming to the hold short line. I have subsequently reviewed the airport layout using Google Earth and see that the hold short line on Taxiway J is immediately past the ramp. I did not see a taxiway location sign for J; a runway holding sign (white on red) for Runway 06 or a hold short line prior to entering the runway. The only reason I can think of for not having seen the hold short line and sign is that I may have been looking for any other taxiing traffic when I passed them. Based on the appearance of the taxiway and runway on the airport diagram; I expected the hold short line to be closer to the runway and farther from the edge of the ramp. I am familiar with the AIM and have previously successfully completed the interactive course 'Runway Safety.' I always thought this could not happen to me. In the future; I will try to have a better plan of expected taxi around unfamiliar airports and be even more vigilant of airport signage.