Now it's time
to tidy up our orbit and prepare to leave Earth. There are three things we
need to do. One is to eliminate the remaining inclination between our
current and our planned
orbit. We also need to ensure that we arrive at Periapsis again at around the right time
in the future - leaving Earth at the wrong time introduces quite a bit of
error. The third is to tidy up the small difference between our
current orbit's periapsis and that of our planned orbit. All of this can be
easily done by entering an elliptical orbit.
One thing which really does matter from here on is accurate flying. If you leave Earth in a different direction from planned, you will consume more fuel later trying to sort things out.
The important thing at this stage is to ensure that periapsis on this elliptical orbit is slightly before that of our planned orbit. The MFD opposite shows when I applied power just before the planned orbit's periapsis. I was actually slightly late.
I then used the orbit MFD to judge how big the orbit should be. Ideally, one orbit of the ellipse should take up almost all the remaining time before our planned MJD comes up. The time T for a complete orbit is what you need. One day =86400 seconds, if you need to convert.
I often create this ellipse as a flexible way of timing my arrival at the next periapsis. They can easily be much higher than this one - I often use an orbit with a T as high as 120k (about a day and a half).
At the other end of the orbit, velocity has dropped to only 2.298k - less than half the velocity I had in low Earth orbit. At this point, I clean up the remaining error in my relative inclination, which costs me much less rocket fuel at this much slower velocity.. Right at apoapsis, a small tweak to the energy puts Periapsis at exactly the right altitude.
Now we simply
wait until we come back towards Periapsis once more. Everything is now
almost perfectly aligned. Ideally the periapsis of the ellipse should be
encountered very slightly before periapsis of the planned hypothetical
orbit.At this point, there's one important thing to do that you won't have time for later. Switch views (VW or shift w), and select the variable called "Intercept with". Change it from its current value (hypothetical) to 'craft'. This will cause the targeting information to be taken from your craft's orbit rather than the hypothetical one you were using earlier.
It was at this point that, with prograde autopilot selected, I applied full power. It's time to leave the Earth behind. You should apply power at the moment that you think is best to ensure that your final orbit is aligned perfectly with the hypothetical one.
The effect of
applying power quickly becomes dramatic. The orbit of your craft around
Earth elongates progressively. Soon after this point, you achieve escape
velocity. Your orbit around Earth becomes hyperbolic. 
Once your
orbit becomes hyperbolic, the view will change suddenly to something like
this. Things at this point happen quickly. Select the other view of your
orbit IMMEDIATELY using the VW button.
You can do this earlier if you choose.
When you do
this, you will see a green orbit growing rapidly away from Earth.This is
the projected orbit of your craft ! Now you will see why we switched the
targeting system over earlier. As your velocity grows, things will quite
quickly come to resemble the target that we set up so carefully earlier.
When things look as if they are coming together nicely, turn down the
thrust so you can be more precise. Turn the engines off altogether when
everything is as aligned as it will get at this stage. You are on your way to Mars!
Typically there will be some error in your path. Don't worry too much about it at this stage - you'll get to sort it out later.