First ,
     Keep your tools clean , once it sets up  water doesn't clean off concrete , wear gloves and use a stiff brush and the hose , watch what you're splashing , if left on a wall it can stain it , if left on your tools , they won't come clean or work as well .
    When it sets concrete becomes a rock similar to a coarse sedimentary stone with the softer portland cement holding the harder gravel and sand mix together.
    Although I have used a tape measure case to smooth concrete , to get a good job you need good tools and good tools aren't cheap  plan on spending $50 - $100 for the basic 4 tools , and more for larger job tools .  Click on the tools for how to use them .

A screet or screed board is just a straight two by four that is moved in a bouncing and sawing motion along the forms to even out and level out the surface of the pad of concrete . The length should be a little longer than the width of the forms and it may be nice to have different boards for different areas of size .  Be sure to pull up and center any mesh before or while screeting the form .

The hand float is used to continue smoothing the concrete  after using a Screet board to level it to a ruff surface .
the float helps press the rocks down into the concrete and raise the cream to the top so the trowel can then smooth it out and remove any bubbles left in the surface .  it is also used to level the surface adding more concrete where needed and smoothing it in .
    by moving the float in an arc over the surface it will tend to catch the high spots or gouge  the edges of the holes or low spots  and help you find them so you can even them out by adding or removing concrete as needed .
if an area is stony or dry you may be able to help it by beating it lightly with the float or and edge of it to drive the stones down ,  then floating it out again .

The Trowel  is used to smooth and polish the finished surface of the concrete .
it is drawn over the surface while twisting the front edge up as the rear edge
presses down against the surface smoothing it in an arc .
the trick is to rock it to keep the  leading edge up so it doesn't gouge the concrete you've just
smoothed as you move it back and forth over the surface and slide it as you raise it up ,  never pick
the trowel straight up , because it will leave a ruff surface on your concrete .

Concrete does not bend well so you need to provide places where it can .
This is done by using a Joint tool to provide a crack to break at just like in a
candy bar .
The spacing is about two times the width of your surface , up to twelve foot square .
you can make the blocks bigger , but you should consult and engineer before doing
it because of the expansion and contraction caused by temperature changes .
You can also concele the joints by smoothing to the joint while leaving the cracks .