I've read several articles that claim that washing your hair with shampoo everyday dries out your scalp and hair. Some articles will tell you to shower about once a week, and others might say shower about twice a week. Really, I think it depends on how active you are—for example, if you workout every day, and what your skin type is (dry, oily, mixture). I am no dermatologist, so please take what I say with a grain of salt. This is my opinion and experiences I am sharing with you.
The most often I will shower or shampoo my hair will be about once every two days depending on what my week is like. If I'm working out hard and sweating bullets at the gym every day, I need to at least wash my body every day, but I'll try to only shampoo every other day to help save my hair. On the days that I don't touch my hair but it's starting to look a little greasy, I have a couple weapons I use to make the grease practically disappear. My lucky dry shampoo and baby powder. If you've never used either, please don't judge. They really work wonders!
Personally, I like using the baby powder more often than not, because there's not as many ingredients in it. I find that as great as dry shampoo is, there's a lot of chemicals in them and I don't like to use them a lot because of that, but to each their own. If you love using dry shampoo, then go for it! The dry shampoo you can buy at your local drugstore tend to smell a little nicer than the baby powder, but once again, up to you!
If you've never used baby powder or dry shampoo before, it's really easy to apply and use!
For either, you want to put/spray the product by your roots where it's shiny or looks greasy. If you have dark hair, don't use too much or it'll make your hair look grey or white. Just use a small amount to start! Sounds weird, but I swear they suck up the grease! I don't know how but it does.
I usually will rub it in, from the roots downwards in a stroking kind of motion you might give your dog. Other times I'll rub it in in a circular motion. Really, it just depends on how bad the grease is, or on the day. Some days I think that the regular up and down motion would work best and others the circular motion would do a better job. It varies.
Like I stated before, you should be careful not to put too much on that it will turn your hair grey. This is worse for those of us with dark hair like brown or black. It's not such a big deal for blondes. When I was blonde I could lather it on and it didn't really do much for changing the color of my roots until they started growing out.
One time I accidentally dropped a bunch of baby powder on one part of my head and I tried to rub it in quite aggressively. It was pretty grey...as I rubbed it in a little more, some of the grayness started to go away, but not all of it. At this point I just put a ball cap on. It was a lost cause.
When my hair gets so greasy that even baby powder or dry shampoo doesn't do much to it, I just give up and wear a baseball hat for the day. Ha-ha, I still want to go out, but not wash my hair yet. It's too much work sometimes and I just don't have the patience or time for it. Then with the ball cap on, I don't do anything with my hair. No straightening, no braiding, I just leave it the way it is (but I do brush it so it's not a crow's nest).