How to practice mindfulness

How to practice mindfulness during the day? I have been know known to be absent minded and forgetful but perhaps it's due to my Karma. The problem is so bad that is someone else makes the mistake due to their mindlessness I am automatically blamed without knowing the facts!!!!! I have been told that meditation clears out ones' Karma and that mindfulness during the day is another form of meditation (I already sit on the floor Burmese pose 30 min twice daily and breathe in, breathe out) How to gradually start being mindful? It seems rather overwhelming .... Thanks!