Saucha, the first of the yogic niyamas, refers to the cleanliness of our bodies and our surroundings. It also refers to what we put into our bodies or our minds: what we eat, what we watch, what kind of conversations we engage in, etc.
The first step to creating saucha in ourselves is to have a real sense of what has a positive effect on us and what does not. Of course, we could all name the things that we "know" are good for us and those that we "know" are bad: broccoli=good; ice cream=bad; inspiring conversation=good; gossiping=bad. However, having an intellectual understanding of what is good and bad is not likely to really affect our choices or change our habits.
Personally, I only feel motivated to make a change when I have felt sense of what has a positive effect on my body and mind and what has a negative effect. For example, after enough experiences of watching stressful TV shows at night and going to bed feeling agitated, I decided not to do that anymore. I have had enough experiences of not getting enough sleep and feeling overly emotional the next day, so I generally try to get enough sleep, or at least when I don't get enough sleep, I know what’s going on and can resolve not to pick any fights that day. Lately, I have begun to notice more subtle things. I have begun to note a correlation between a sense of anxiety and the cup of coffee I have taken to having in the afternoons. It doesn't always happen, so I haven't said "goodbye" to coffee altogether, but if I am already feeling wound up, I may give it a miss, or if I do have it and anxiety arises, I no longer feel confused about its cause, and I know it will pass. I have also begun to notice that when I have a carb-heavy snack in the afternoon, which I often do as carbs are delicious and filling, I later have an energy crash. Again, this doesn’t necessarily mean I never have toast as an afternoon snack, but I know what will happen, and I try to choose snacks with more protein instead sometimes.
The more we notice the effects of different things, the more information we have, the more opportunities we have to make better choices. If you want to practice saucha from the perspective of mindful consumption, I encourage you to notice the effect that the things you consume-whether it is food, drink or media-have on your sense of wellbeing. Or if you forget to do the preemptive noticing, maybe take a moment when you find yourself in a particularly good or bad state, physically, mentally or emotionally and see what preceded it. You might start to see some patterns: when I eat sugar, I feel energetic for a short time but later feel cranky; when I listen to music, I feel good; when I smell peppermint, I feel energized. Such information can help you be good stewards of your own wellbeing.