I'm probably not the one you will find the most reliable givin my dxm topic lol but the theory goes like this:
You first need to develop concentration meditation in order to be able to advance in insight meditation, witch is the one that will get you to enlightment. I have read that therevadian westerners like these on this forum have difficulty advancing at vipassana because the way teaching goes in the west is based on the burma tradition where they seem to jump a little over the samatha because people there are way more advanced at concenration than westerners. The very complex and speedy way of life in the west makes westerners bad at concentration.
The Budha thaught both methods and said that you should atain the first 4 jhanas to be able to advance till the end at insight meditation (witch has 16 nanas). The descriptions of the jhanas/nanas are not perfect because the map is not the same as the path but they are usetfull and pretty acurate.
You will be guided to vipassana meditation on this forum because it is therevada. Probably it is recomanded to practice both styles every day in 2 meditation sessions one for each one. I would like to hear from somebody advanced too.
As a side thing... the "interesting stuff" that motivates a little all of us beginers whether we admit it or not (because you say oh it works, it finally works)(advanced meditators avoing talking about this to not make you deluded but I think any beginer needs this as a little extra motivation beside the horible implications of not escaping samsara) happens in samatha meditation but the arising and passing away event witch is the most powerfull experience a person can feel in his life (in terms of oh my god, oh my god) althow been just the 4th nana happens in insight meditation. Also enlightment happens in insight meditation and althow not having pleasant effects like jhana little "revelations" about the nature of things witch change you not just for the moment also happen there.
edit: maby this guy helps viewtopic.php?f=41&t=17253