Most bikes are built for men 5'4" to 6" (and as you approach these limits you start to see the problems. The reason for this is the Average height for males is 5'8". Four inches either way is an easy adjustment. More than 4 inches you HAVE to go to a different frame size (and it is better for people below 5'6" and above 5'10" to go to a different frame size).
Now there are other adjustments you can do:
1. Crank shafts. The Standard Crank Shaft is about 170mm, longer ones help taller people, through shorter ones seems to have no affect on shorter people. For more see the following
http://www.sheldonbrown.com/cranks.html2. Longer Seat Posts. This has the affect of pushing the rider backward a while as up.
http://www.sheldonbrown.com/harris/seatposts.html3. Stem-posts changes: I have done this myself, installing an extension to the stem-post to raise the handlebars.
http://www.sheldonbrown.com/handsup.htmlNotice most items relate to helping taller people ride smaller bikes. The reason it is easier to ADD height via the above adjustments then to SUBTRACT height. Thus it is more important for SMALL people (People whose height is less then 5'4" and probably anyone under 5'6") to get the right size frame.
A related problem is your sex. Most Women are smaller than most men (There are exceptions both ways, but this is the general rule). Second the center of Gravity of both sexes is different. This is mostly based on where the muscles are located in each sex and that fact Muscles weigh four times the same volume of fat. A man's center of Gravity is in the middle of his chest, where most of his muscles are located. A woman's center of gravity is also in the middle of her most powerful muscles, the most powerful single muscle in any either sex, the muscle to push out an infant when the infant is born (Thus the lower set of "Curves" on women, for the curve is this muscle, a woman's mammary glands are most light weight fat and while the head has a heavy protective shell, the neurons inside are even lighter in weight).
Given the location of the center of Gravity in both sexes are different, how each sex rides comfortability on a bike is different. Men whose center of gravity is between the handlebars and the Seat tend to move the bike with there whole body, women whose center of gravity tends to be up in the air prefer to sit more upright (i.e. OVER their center of Gravity). A lot of women like recumbents for it puts their center of Gravity close ot the ground and they can move the recumbent almost as quickly as a man can move an upright bicycle.
I bring this up for when fitting a bicycle you have to consider adjustments that makes you more comfortable given your height and Center of Gravity.