Leonard's post about using less than top of the line bikes for touring is how I started too. My first tour was a 4 day tour as a preteen with my then teenage brother through the French countryside in 1973. Our parents had arranged for a place to pitch our tent in the courtyard of the farmhouse belonging to one of my dad's colleagues. We then went on day rides on our high tensile steel Peugeot UE8 that came decked out with steel rims, Simplex derailleurs, mudguards, lights, a carrier and a low gear of 47/26.
That remained my touring bike until 1979 when I assembled myself another one with Champion n°2 tubing, Campagnolo derailleurs, Ofmega cranks, Diacompe brake calipers with Modolo levers and Scott Matthauser pads, 3TTT bars and stem, Dura-Ace large flange hubs and SuperChampion rims. The bike weighed in at 10 lbs less than the Peugeot. This is the bike that I spent 8 months touring through the US, Canada and Mexico on in 1980-81. I traveled with Cannondale panniers attached to a Blackburn rack, a handlebar bag and a saddle bag. It was also fitted with Bluemels mudguards, a Sanyo BB generator and lightset. I was ready for all weather with a full complement of wool clothing, a first generation Gore-Tex jacket, a Gore-Tex bivouac sac and shoe covers. As far as gearing, I had what I thought back then to be a low gear of 42/24 (lower than what I had ridden on the Peugeot).
The third was a custom-made Marinoni which was actually a racing design with the only concession to touring being the dropout eyelets both front and rear and further eyelets for a carrier on the seatstays. With judicious use of an exacto knife, I was able to make a set of mudguards fit. I toured through 9 European countries on this bike. The touring gear remained the Cannondale items of 1979.
The fourth was a frame that I built myself. This too was more of a racing frame. By this time I had learned the advantages of a low-rider front carrier and therefore toured with front cannondale panniers on the lowrider blackburn rack. To add sufficient carrying capacity, I added an Eclipse SPT to the seatpost that allows the fitting of two handlebar bags, one under the saddle and the otherup front. This was sufficient carrying capacity to allow me in 1985 to ride 3200 km from Amsterdam to Yugoslavia and back, stopping over to watch the World Championships in Bassano del Grappa in Italy.
My suggestions for touring are therefore to first reduce what you are carrying to a minimum (Harvey's suggestion about credit-card touring is good!). Put out what you think you might need, then put half of it back in the drawer. Pack your panniers and then remove 50% of it. While the use of a proper touring bike is indeed helpful, it is not needed if your fitness level is there.