1. Only wash your scalp (not the mids and ends of your hair) as this is the area that produces the oil. Try using a shampoo low or free of sulfates.
2. Don't condition everyday or if you feel you must do so only condition the mids and ends and avoid conditioning your scalp all together.
3. In between shampoos try a dry shampoo. Dry shampoos when applied to the scalp will absorb oils and give a "just washed" look to oily hair.
4. Avoid applying styling products to the top/scalp. Styling products are heavy and usually contain oil. Apply to mids and ends and avoid product with oils. If you are in need of an oil based product (most commonly found in moisturizing products) for the dry ends of your hair do just that, apply only to the ends of your hair.
5. Wash your hands before styling your hair. Depending on your routine you may have product buildup or if you are like me and put on lotion/makeup before I style my hair you definitely need to wash your hands so you are not adding more dirt and oils to your hair during styling.
6. Switch your products up. A common mistake is using the same products over and over everyday. Your hair will have different needs based on styling, climate/environment, chemical treatments, etc. If you color your hair regularly use products for color treated hair. If you live in Florida like me (with high humidity) use products meant to counteract days with high humidity but on days with lower humidity, ditch those products for the day. If you need moisture, use moisturizing products but have some substitutes for in between such as a reconstructing treatment. If you are blowdrying, curling or flat ironing... always used a product with heat protection. Overheating your hair is the #1 cause of damaged hair. If you are going over your hair more then 1 time with the flat iron then you need a new iron or the heat is too low.
I think that I covered most of the common no no's when it comes to washing and styling. If I left anything out or if you have questions about something that I did not cover then please don't hesitate to ask! Happy hair care to you!