Natural means are limited...
Healthy diet - better diet will help a lot, even changes to diet leading up to your period will help, make sure you're getting iron to make up for blood loss, magnesium, zinc and calcium for menstrual health, vitamin E to regulate flow, and vitamins A and C to regulate estrogen levels to lessen flow.
Stay stress-free - cramps and flow are effected by emotions, stress is the biggest emotion to effect your periods so avoid it wherever possible, also your feelings towards menstruation makes a difference, women who feel more positive about menstruation not only will be more likely to learn about menstruation so learn how to better cope, but generally do have better periods.
Regulate hormones - if you're in your teens your hormones will be mental, but you can help keep things regulated, diet and generally staying healthy comes into this a lot, but also taking evening primrose oil or black cohosh daily will help a lot too.
Herbal treatments - coffee is a good way to lessen flow as it is a vasoconstrictor so constricts blood vessels in the uterus preventing heavy blood loss. Look into herbal treatments like chaste tree which is well known for helping with heavy flow, also drinking either vitex tea or a women's blend will help.
Menstrual cups - these make periods easier to manage as they can be worn any time of your cycle for up to 12 hours, hold more flow, and don't leak like tampons and pads do. Menstrual cups can also in many cases lessen cramps and menstrual flow.
Women don't have to have cramps, most women can totally prevent them if they only learn how, and as for periods, there's nothing wrong with periods and yes being able to have children is one plus, but also periods can bring other positives such as sex being a lot more enjoyable, and women can experience other positives such as fuller breasts, better concentration, and a whole host of other positives.