Most people are usually living either in the past or in the future by thinking about the past and imagining the future.
It is important that you live in the present moment by being witness to, the perceptions of your 5 senses now i.e you must be aware of your environment, what are your hearing, smelling, touching, seeing and tasting (if eating). While being mindful of your observations in the present moment, DO NOT BE JUDGEMENTAL, be in the witness and acceptance mode.
Innumerable times in my past, I have done activities, of which I rarely remember any details, such as driving without having noticed the beauty en-route, eating without being mindful of the taste of the food and so on. However, over a period of time, I have practiced this living in the moment exercise a number of times in the day and slowly, have now fallen into that mode of Living in the moment.