This tutorial will show you 2 methods of modeling, the one described above and modeling relatively complex objects form a cylinder using one of my favorite blender features the loop cut!
For this im using blender 2.64
This is useful for modeling symmetrical things like bullets, lamps, pillers, table legs exc
Step 1: Blender
Step 2: Adding the Shape!
in the second pic you need to set the number of sides to 8 and no caps on the end (not necessary for this one but is a good habbet to have!)
Step 3: Scaling and Edit Mode
this is done by first hitting S for scale and than Z to scale along the Z axis than clicking to hold it!
Next we want to enter edit mode and get ready for our cuts ... hit tab to enter edit mode and than hit A to select nothing
Step 4: View and Cutting!
now time to make a loopcut ... click ctrl+r than place your mouse over the object, a line should appear in the middle of it, click and set the place where you want the cut to be than click
now hit S and move your mouse to scale it as you want it to be!
do this untill you get a low-polly version of what you want
Step 5: Smoothing and Fixing!
next exit editmode with tab click "smooth" under shading and enter edit mode again to see your crisp new model!
but it looks all ... meh ... next we fix that!
Step 6: Fix the Meh!
lets make more loop cuts ... this time you want to make your cut above or below the eadge you want sharper ... click on it than drag it up the curve and you should see it sharpen up, click to apply, do this below it also and repeat anywhere else you want to do this!
Step 7: Cap Those Ends!
select the end, do this by holding down alt and selecting an edge on the loop you want to select and you should select the entre thing
now hit E and you should see it dragging a clone of the selection ... right click to put it back! ... without selecting ANYTHING ELSE hit ctrl+m to bring up the merge menu and select "collapse" and you have your cap! ... repeat it at the bottom