You change it according to your flow. So I guess for me it's usually every 2 hours when it's heavy and towards the end of my period, it's every 3 hours or so. Ofcourse at night it's longer so you can use a longer/thicker pad. I use tampons as well and those i change quite frequently but with working out those are the most comfortable. With the tampons you can just flush them down the toilet. With the pads you can wrap them with the plastic wrapping they come in(usually they just stick to the glue of the pad) or you can just wrap them again in some bathroom tissue. You can toss it in a different trash bin if you dont want someone seeing it in the bathroom:)
And the washing of the cloth thing. People still do that in my village, it's not a matter of being from a "lower class." It's just that living in the village it's hard to get pads and what not. Forget about pads, you're lucky if you get pre-packaged food. It's not a matter of being from a lower class but of where in pakistan you live. My family for example is well off but my aunts still do this. However, they don't wash it but instead just burn the dirty one. They also do it because the place where all the garbage is disposed is frequently looked by searched by children and even men looking for clothes and what not. They don't want them having to step on it and wondering what the hell it is. Not to mention, having men seeing it is quite disgraceful in their sense and i respect them for that:)