1) Sanding Prep- before painting it is best to sand any rough surfaces of your wall to get that smooth professional look.  You will want to use a fine grit sandpaper.  When sanding oil based paint you will want to use a medium grip-100-150 sand paper. Make sure to remove any dust before painting with a damp sponge and allow time to dry.
2)Always use high quality paint and supplies to ensure longevity.

3)Use canvas drop clothes, not plastic or thin bed sheets on your floors to protect them from making.  Don't use plastic or thin bed linens as they can seep right through, and plastic covering will only be slick and prevent the paint from drying. Drop-clothes are more expensive, but is worth it to invest in.

4)Use tinted primer

5)Apply Painters tape to all wood trim and use a putty knife to push in the tape.  Painters tape is used for the baseboard trim.  Using a putty knife push on your tape in a straight line.  Lay only small sections of tape at a time to keep your line straight.

6)Use Paint extender because it slows down the time it takes for your paint to dry so that you can paint over newly painted areas so that your sections will blend well together. 

7)You do not have to tape the windows! Instead when they are dry scrape them with a razor knife.

8)At the end of the day don't forget to bag the roller! If you are not finished painting but are done for the day, what do you do with your rollers and brushes? Soak your roller in your paint and  cover it tightly with plastic. This will ensure your roller stays fresh until you need it again.  If you are waiting longer though, you will want to throw away the old roller cover and use a new one when you pain next. 9)For your brushes, rinse them off  with soap and water unless you are using latex paint and in that case you will want to use paint thinner and make sure to cover the brushes in newspaper or another type of wrapping.

*pro tip: If you are painting the top of a wall with a popcorn ceiling, use a screwdriver around the perimeter to scape off some of the texture.. This way, you are able to easily cut around the ceiling and not get any pain on your ceiling.

*cover your paint bucket with a damp towel when switching between brushing and rolling so that your pain won't dry out when you are not using it.