One method of pattern making is to make a "cast" of an item.
Say you want to copy a coffee can. Wrap the coffee can in plastic wrap. Then take duct tape and tape the entire body of the can, overlapping the tape strips by at least 1cm. Make sure you cover then entire outside.
Make reference lines. Using a ruler, make vertical lines and a few perpendicular ones to that line. These lines will be helpful when you go to make your pattern. Run a horizontal line around the bottom of the can. (typically this line is about 1/2 cm up from the bottom.) Make short vertical reference lines. I should say that it helps to use one color marker for the main cut lines, and a different colored marker for the reference lines.
Cut the cast from the can. Cut the bottom off the cast. Open the cast up and lay it flat on pattern paper. Pattern weights are helpful here but you can use canned goods to hold this in place. Now, trace around the cast piece an transfer the reference lines. Remove the cast piece... and measure your seam allowance what ever size you feel you need and use a ruler to mark your cut lines and to extend your reference lines.
Now a coffee can would be fairly easy to cast. When you get into making patterns for a body part, you'll deal with having to make a 3D cast into a 2D pattern. This is why the reference lines are so important. You'll need to take several tiny tucks to make a 3D cast lay flat so you can trace all they while trying to not lose those reference lines. This is sometimes called easing.
I think by now you have a general idea of how to cast and pattern objects. Have fun practicing. May I suggest you try this on your feet?
BTW... use a decent quality duct tape to do this... the cheap stuff is a pain to work with.