There are a number of different types of lipids; waxes, phospholipids, fats, and steroids.  Some of these sub-groupings are more commonly connected with food and nutrition than others.  

Which sub-groupings of lipids should really be looked for?

Is there a difference is testing for saturated or unsaturated fats?

There are definitive chemical tests that show the presence of fats, but are there some ways to test for fat with everyday materials? (Think about pizza for this one!)