First of all, I am not a professional or expert photographer which probably makes me just like many of you here.  I like to take pictures that I will enjoy looking at....mainly relating to family events.  Wanting something better than a regular point-n-shoot camera, I bought a Canon 400d with the standard 18-55 lens.  Great pictures straight away!  It was clear though that I really wanted to be able to zoom in much further. 

Brief laymans explanation of the numbers.......difference between the numbers describing the lens relate to the range of zoom.  18-55 isn't really that much.  18 is wide angle, suitable for landscapes or maybe someone standing close to you.  There are wider lenses but 18 seems to be a fairly standard starting point.  The higher number relates to how much you can zoom in.  The 55, explained very basically, seemed to be good for zooming into someone about 5-10 metres away, maybe on the other side of a room. 
Examples of various zoom lengths (from a cameralabs.com review):
17 (didn't have an 18!)


28


50


100


200


300


Main lens options I looked at:

• 70-300 - Good value and being able to zoom to 300 would be great.  Information I could find says that you really need a tripod once you zoom past about 200.  Main problem for me was that I would have to change lenses, between the 18-55 and 70-300.  This doesn't have to be a big deal, but I'd prefer to just carry one lens.  Changing lenses also increases the chances of getting dust inside the camera.
  
• 28-300 - This looked like a great solution until I discovered that the zoom difference between 18 and 28 is significant.  Starting at 28 means you are already zoomed in enough to affect many pictures.  See the examples above.
  
• 18-200 - Now we're talking!  A lens that starts at the same wide-angle point as my other lens but goes all the way to 200.  Not cheap, but so far has been great.  It's hardly any longer than the original.  Suddenly, I can take a group shot but when I see an individual doing something in the group, I can very quickly zoom into them and get some great pictures.

Most photographers, amateur and professional, will take good care of their lenses so a second-hand item of this quality is likely to in good condition.  Of course, you still have to check this with the seller!  It still won't be cheap so check the obvious things....feedback, seller helpfulness, returns policy, payment protection.

Hopefully you found this guide to be of use.  If you did, please click the 'Yes' button below.....ahhhh, go on!