Body Fat

You can get skin-fold calipers on amazon for pretty cheap, which are used to take measurements from different places on the body... unless you have actual training doing this however it doesn't seem very reliable.

They also sell scales (walmart has them) that will tell you your BF% by running a current through your body.. but these tend to be heavily influenced by how much water is in your body, how you're standing on the scale, etc.

The most accurate way to tell your bodyfat percentage is to go to a doctor / clinic that has specialized equipment... though I'm no doctor so I couldn't tell you more about how this works.

Personally, I just use a scale-based BF% calculator as a cheap, easy to use progress indicator. I'm sure my bodyfat is way off from what it says, but at least this way I can keep track of my gains and losses relative to my previous weigh-in, even if the numbers aren't accurate.