I cannot tell you what bike to get, any more than I can tell you what computer to buy, shoes to wear, or coffee to drink. Instead I will give you a few parameters and things to look for, and have these added/installed on the bike if they are not already present. The final decision on what bike you choose must be yours: your bike shop will help tailor you and your bike so that the frame size, among other things, is correct. Just keep in mind the following.
- Buy the midrange of prices: Too cheap and the bike won't handle the strain and be durable enough. Too expensive and you will be paying for bourgeois features that bicycle touring ( a very proletarian activity) doesn't need. The latter is the most common error new touring cyclists make. For example maybe for $200 you can get a spiffy frame and lighter components. But its cheaper to take a few pounds off your fat ass (and alot more healthy, too!) And fancy parts train may not be available in the back of beyond, anyway. Hydraulic brakes for example. Forget them! Keep your bike simple and it will be easier to find parts and replace them.
- Get randonneur style touring handlebars. These offer the most comfort and the greatest variety of hand positions. Look at the six small photos below to illustrate this. Mt. bike style handlebars do not offer the same choices. Even if you buy a mtn. bike (more about this later) have the touring handlebars installed.
- do not get shift levers that attach to the brake levers. Great for racers, they are expensive and not as durable as fram attached shifters. I prefer my shifters on the handlebar stem. On this world tour I had them at the end of the handlebars, but I did not like this. They were always in the way when leaning the bike against anything. And i had to move my hands more to shift gears, since most fo the time i ride with my hands on the upper part of the bar, not down on the drops. So will you...touring is for sightseeing so you'll want to be sitting more upright than a racer will be.
- Make sure you get gears that are low enough. Expect a fight with your bike shop with this...very few folks have toured long days and long distances, and know how nice those low gears are late in the day, on a steep hill against a stiff wind!
Despite all the chatter over 18, 21 and god-knows-how many gears, the most you'll ever need is probably 12 and that all you've REALLY GOT with a "18 speed" anyway, because of the gear crossovers that you really shouldn't use. On my old fuji S-12-s, I added a third chainring and had 52-39-28 teeth in the front. On the freewheel I had 14-17-20-24-28-32. Thus I had two gears that had a ratio of less than 1, and many low gears overall. There were only 2 or 3 gears that I would call "high" gears that I used for riding with the wind to my back or down a long, gentle hill. (I coast down steep hills and brake frequently). On my world tour this time, the front was 46-36-26, and the seven cassette freewheel gears had 11-13-15-17-20-24-28. I did not like the 11 tooth gear, it gave a grinding sensation even when used with the biggest chainring. In any case by the time I reached Asia the front chainrings had worn out and I could only replace them with a 52-39-28 set (all they had in eastern Turkey!). Nor did they have cassettes, so I had to buy a new, smaller freewheel with only 6 gears 12 thru 26. As a result I lost my beloved granny gears for a while!
Whatever the specific gears you end up with, make sure that the gear you normally tour or ride in is 3 or 4 gears from the top, maximum; and leave 7 or 8 or somesuch gears below that, including the very low 'granny gears' I mentioned earlier. Your knees, thighs and lower back will thank you for it.
- If you are quite tall/and or have long legs, consider getting crank arms that are longer than the standard XXX millimeters. Like the old cigarette ad, those silly 'extra millimeters' can make your pedal stroke much more effective and comfortable. For tall folks some mountain bike crank arms are like getting on a tricycle for a three your old!
- To carry your panniers on the bike you'll need racks. I say Blackburn racks, front and rear. I have toured with blackburns for years and never had one break or come unattached from the frame. I don't know how people who break them do it! Maybe they imitate Evil Knievel? In any case..the front rack should have a metal panel across the top; the rear one should have just the frame.
A few years ago cyclists and magazines hyperventilated about Japanese made "low riders" or racks that carried your panniers much lower and close to the axle. These died out, thank God, for several reasons. First, on the front you miss the valuable space on top of the rack (thus the panel) for lightweight but awkward cooking gear. Don't put cooking gear in your panniers...its not crushable and takes up alot of space! Lash it to the top front rack with two small shock cords (see photo below).
Second,on the back low riders deny you a place to put your lash your camping gear: tent, foam pad, and sleeping bag!
Thea argument is having weight near your axles makes the bike more stable. But if you are that affected or concerned by weight and its distribution, you are probably carrying too much! Again...a few pounds off the CYCLIST will make a far bigger difference!
- Panniers...ah...panniers! Here, as with raingear it is important enough that I provide a product review of my Ortliebs (Yuck!) that i chose for this world tour. To save you from clicking now, the problem with 'totally waterproof panniers' is quite simple: what goes in wet stays wet, and often mildews in hot damp weather, to boot! What you want are medium sized, water resistant, smartly cut (rectangular) shaped panniers with several big zippered compartments and a few nooks and crannies as well. My all time favorites were my Kirtland Tourpacs: 2 large compartments for clothes; and smaller compartments on the front, side, and back for quick access to things like tools, raingear, food and snacks, etc. For tips on rigging the panniers to beat the rain, see the next section, 'Life on the road.'
In any case: don't get panniers that:
- have an awkward or tapering shape (Ortlieb)
- have one big useless compartment where everything egts stuffed and lost (Ortlieb)
- are not smartly cut in the back to avoid your heel hitting them (Ortlieb)
- attach to the racks in some bizarre fashion. Bungie/shock cords and/or springs are best. They absorb the bumps and bruises of the roads without the infernal rattling I listened to for 2 years with, you guessed it...my Ortliebs!
- Toe clips or clipless pedals are a choice up to you. I have done 8 tours with a total of 4 years on the road, and nearly 100,000 kilometers in all types of terrain. For two of these trips, totalling six months, I wore toe clips. I don't recall being able to do anything I wasn't able to do before...and I hate the sensation of being clipped in. The advantage of 'pulling up' clips give you is vital to racers. Whether it helps touring cyclists is very debateable. I see long distance cyclists without clips fairly often.
- An odd last comment. Mountain Bike or touring bike? I'll oversimplify...this issue will be discussed alot by my readers I am sure. If you are traveling in Europe, North America or most of South America's coastal regions, a touring bike is unquestionably best. The roads are paved, smooth, and even the dirt roads are quite decent. You'lll waste time and energy pushing fat, soft mountain tires on good tarmac.
In contrast, in Asia the term 'pavement' can really be a misnomer. In Pakistan, Laos, Cambodia, the interior regions of Vietnam and China, and many other places the roads are awful to pathetic! Here a mountain bike is probably a better choice for comfort. The frame and rims are more rugged and durable to boot!
For me this meant on my world tour, my touring bike was great in the Americas and Europe. When I hit Asia I often wished I had a mountain bike, but stuck it out through the tough stretches, anyway. You will find that you become very attached to your bicycle afetr you have ridden it on a long tour..it is like a loyal friend that sees you through the good and bad times. Like a cowboy with his horse!
A few more helpful comments before I finish this section. 
