A CRJ-900 Captain reported deviating from the charted course on departure from DCA; citing failure to brief and properly set up navigation systems as contributory factors. Fatigue was also a factor.

Narrative

On departure from DCA off Runway 01; we made the initial turn to follow the Potomac River to the northwest per the noise abatement and prohibited area avoidance procedures. The cloud cover was approximately 800 FT broken; so I planned to pick up the DCA 328 radial. I knew my heading was good for avoiding the prohibited area; so I patiently waited for the radial to come in. After a minute or more; when it seemed like the radial should've come in and I still had a needle deflection to the right; I turned 5 to 10 degrees right to intercept the radial. After another minute; I turned another 5 degrees right; but started suspecting that something was not set up quite right. There was a slight crosswind factor from the right; but it did not seem like it was significant enough to require this amount (15 degrees) of intercept angle. Approximately 5 minutes into the flight; Potomac Departure asked us if we were still following the 328 degree radial. The First Officer responded in the affirmative. While I was not picking up the radial (I mistakenly had a localizer frequency set in NAV #1); the First Officer had set up the DCA 328 radial on the Fix page of the FMS. We believed we were close to the centerline. I had the scale on my PFD too far out for the picture to be accurate. The Controller said we looked to be about 3 miles north of centerline and assigned a heading of 300 degrees to intercept. I finally got the correct frequency entered in NAV 1 and returned to the assigned course.Several factors led to this deviation from course. 1) Insufficient crew brief: I completely failed to cover the course I would fly after takeoff. I did not brief the noise abatement procedure for DCA. I did not include the information that I would fly the green needle with the DCA 328 radial set in. Had I briefed this properly; the frequency and radial would have been set up properly before we even left the gate. Instead; it occurred to me as we were taking the runway for takeoff that I would need to be in green needles with the DCA 328 radial set in. I briefed this while taking the runway; clearly not the right time to do that. I said that I believed the frequency to be 111.0 and the First Officer responded '109.9;' which I set in and didn't question. I do not fault the First Officer for the incorrect frequency. The bigger error was not the frequency; but the timing. We were all of a sudden under time pressure of our own making as we were taking the runway for takeoff. 2) Complacency: A) I've flown this departure numerous times and felt that it was no big deal. B) Flight was a reposition flight and the last flight of the day. This may have led me to treat it differently from a revenue flight. 3) Fatigue: While I felt fine and alert when crew scheduling assigned us this schedule change; I started to recognize in flight that I was perhaps not as alert as I should have been. It was our fourth leg; starting in our 12th hour of duty; on a day that followed a reduced rest overnight. Be mindful of complacency; treat every flight the same; [follow] SOP always. An improper brief and setup led to this deviation. Upon realizing that the navigation was not properly set while taking the runway for takeoff; we could have taxied off the runway to setup properly.