Usually a 5 minute bike ride at a steady comfortable pace, or a brisk 5 minute walk, is enough. A cool-down is just the opposite. You want to gradually slow the body down. Stretching also makes up a part of the cool down. Beginners, as well as advanced, should stick to the basic exercises.
Rest is very important.
A beginner should also exercise the whole body. Beginners also need to find the correct weight to use. Generally the weight should be heavy enough so you can do 10 reps, with the last couple being pretty tough. If you can do 11 then raise the weight slightly. You should keep a log and write down the sets and poundages you used.