With meditation I suggest that you slowly lengthen the time you meditate. Start with a short amount of time and add a few minutes each day. Also when meditating you should sit in a comfortable position so you do not interupt the meditation because your leg fell asleep or something of the sort.
With meditation you should do it for as long as you feel comfortable. there's no right or wrong amount of time. with the other basics [like herbs, colour association, and other forms of study] you should try to take about an hour a day to study/read/practice. If you want detailed information on them, you can find books and articles that can help you. Keep in mind everyone's different so if something doesn't feel right, then change it to suit yourself, the books/articles are guidelines.