incrase and decrease height and radius of cylinder

How do I increase (or decrease) the height of a cylinder (without changing the radius)?
How do I increse (or decrease) the radius of a cylinder (without chnging the height)?

Just press N and set Dim values.

Or you can scale directly with keyboard: press s and then press z and move mouse.

If you want scale x and y (that is radius, if you created your cylinder from top view), then press s, then shift z and move mouse.

Or you can use scale-gizmo that is located in the bottom of the 3D-view.

Three ways (that I know of)

- 1) Turn on the 3d manipulator (CTR-spacebar or click on the "hand" icon in the 3d window header
    - set the transform orientation (ALT-SPACE) to NORMAL
   - change the manipulator to scale or combo mode and click and drag on the BLUE square-sizing handle

2)  press 's' (scale), then   'z','z'  (the second 'z' press changes the axis to local/normal
  1. Display the object properties dialog (“N”) and click the “lock” icons on the axis you dont’ want to affect. E.G. for Z scaling only, you’d lock the ScaleX, ScaleY axis, then press “s” and drag the mouse to scale

a) Use the transform properties dialog with the axis “locks” as described above, i.e. turn on the lock for the LocZ axis, then press “s” for scaling and drag the mouse.

b) use the "shift axis locking /selection as described here, i.e. press “S” to enter scaling mode, then SH-Z to lock the Z axis, then drag the mouse to scale along X-Y only