Bad handlebar angle. On drop handlebars, the ends should angle downward five to ten degrees. This flattens the part of the bar behind the brake levers, turning it into a good and comfortable place to put your hands. Never, ever rotate the bar up, so that the ends aim upward of horizontal. It makes the part of the bar behind the brake lever unusable. It makes it hard to hold the hoods. Plus, it feels weird, like a backwards t-shirt or twisted socks.
Brake levers too low on the curve of drop bars. This is more often a problem with older bikes, but watch it on any. The lever body should be high enough to allow you to put your hand on it without bending your wrist. If you put it too high, it'll be hard to reach the lever from the drops. So monkey around with the position if you like, but make sure it's high enough.
Saddle too low. Probably 80 percent of the riders you see, even on $7,000 bikes, have their saddles too low. When your saddle's too low, your knee bends too much at the bottom of the stroke. That's bad for two reasons:
(1) It makes your thighs (quadriceps) fatigue sooner because they're working harder. Pedaling up hills with a too-low saddle is twice as hard as it is with a right-height saddle.
(2) It puts chronic stress on the contact between the backside of your kneecap (patella) and the front side of your thighbone knuckle (femoral condyles), leading to pain and increasing your chance of getting arthritis.
The next thing you know you're fifty years old and hobbling about like you're eighty-eight.Set your saddle height (measured from the center of the crank to the top of the saddle, parallel to the seat tube) 10 to 11cm less than your PBH.
Seat too far forward. It's no good to shove the saddle forward on its rails if your reason for doing it is to make it easier to reach the handlebar. Although moving the saddle forward will shorten the distance from the saddle to the bar, it's best to shorten that distance by monkeying around with the stem length, not the saddle position.The saddle position is for pedaling efficiency, comfort, and power. And the thing is, if you move the saddle too far forward, you'll put more weight on your hands and be less comfortable. Of course, if you ride only about a mile at a time or so, it doesn't much matter where your saddle is.