R' Yakov Haber began the series on improving our Kavannah in the first posuk in Krias Shema and the first brocha of Shemoneh Esrai by discussing what is the necessary Kavannah for Shema.
The Shulchan Orach rules that mitzvos required Kavannah although it is a machlokes in the Gemorra and among Rishonim. The basic Kavannah is that we are doing the act to follow for the purpose of fulfilling a commandment from Hashem. The Chaye Adom has a leniency on this halacha that says if you are doing the mitzvah in its proper context (ie saying Krias Shema sandwiched between it's brochas in Shul) you have fulfilled the commandment b'dieved. However everyone agrees it is better to have Kavannah.
By Krias Shema there is an additional Kavannah required, the we are accepting the yoke of Hashem (Kabalas Ol Malchus Shmayim). This Kavannah can not be fulfilled with the Chaye Adom's leniency.
The mp3 for this 15 minute shiur is here.
