Look Slimmer ... using your scarf

If you tie your scarf so the majority of it lays vertically on your body, it will make you appear slimmer and taller, as demonstrated by Jennifer Aniston:

Too much bulk however, will create volume, where you may not want it: 

 

If you feel you need a scarf with lots of material to keep you warm, try a fabric like this fleece scarf from John Lewis for £7.  None of the bulk and all of the warmth!

Red fleece scarf, John Lewis, £7