As for stars, stick to G and K type main-sequence stars. They're usually painted yellowish in diagrams (guess why).
http://en.wikipedia.org/wiki/Stellar_cla…
http://en.wikipedia.org/wiki/Main_sequen…
Hotter than G and the star won't last long (maybe a couple of billions of years since it begins main sequence) and will require that planets are far from it so they won't "cook". Colder than G or K spectral types, and the planets have to be closer to the star and they might be subjected to variations of a wider range of output from the star (cooking the surface whenever the star "feels like it").
2; The solar system must be quite similar to our own.
Again, not quite a criterium used by the Kepler team, but close enough.
There must be a "central" earth-like planet in the habitable zone, where humans can exist comfortably.
The problem is that the mainstream media depicts the discoveries of new planets very wrongly, by producing paintings which have nothing to do with what the astronomers actually measure. http://kepler.nasa.gov/Mission/QuickGuid… What astronomers often do one of two things:
1) look at the star and wait to see if its brightness varies periodically (sign of a planet passing in front of it); think of measuring the SIZE of a fly that passes in front of a car's fog light by measuring how much the light dims down when the fly passes in front of the car. "Periodically" here means recurring over the course of several days or months (the time that a planet would take to make a full orbit around its host star).
2) if they are able to measure a periodic wobble in the position of the star's spectral absorption lines,
en.wikipedia.org/wiki/Absorption_spectr… they might determine the presence of a (large!) companion (think Jupiter or larger), because that wobble means that the host star is slightly dragged by its companion, so it "moves" (wobbles over the course of the companion's orbital period, measured in days, or months or years) relative to us and because this is effectively a Doppler shift of the absorption lines you can measure the mass of the companion (knowing the mass of the star).