If you have never painted a room before... bravo to you! But there may come a time when you need to paint and knowing where to begin is essential in producing a good quality product that will leave you feeling accomplished.
To begin, you must prepare your walls. This means filling in any holes, removing any peeling paint, and priming. Use a good quality spackling compound that you can pick up from your local home goods store to fill in any nail holes. Let the spackle dry and then give it a good sanding to get the wall surface nice and smooth. If you have any peeling paint you need to use a scraper to remove it and then you can sand down the wall to even out the surface. Finally, you must prime. There are paints available that have primer in them but they are often thick and you will need to do two coats anyway. If you are going to use a dark color you can purchase a tinted primer. Either way, primer evens out the surface of the wall giving you a nice crisp starting point and allows the true color of the paint to show. Primer gives the paint a clean surface to adhere giving you better coverage and even distribution, making your painted surface look its best.
Before beginning to paint, put down a dropcloth to cover your floors. Drips and splatters are inevitable so it's better to protect your floor instead of trying to clean up later. Use painter's tape to tape off the room. This is especially important around moldings and door knobs. You should also remove faceplates from switches and outlets so you get a nice even finish around them when you put them back on. When cutting in use an angled brush and take your time. A smooth cut in line will make all the difference when you are finished.
Use a roller when applying the paint. Rollers are usually labeled as to what type of surface they are best suited for, so choose the one that corresponds with the surface you are painting. Using a roller will also expedite painting and eliminate lines. Make sure when painting you use a v-technique and overlap as you paint so you do not get lines between sections. You can find tutorials on how to paint on the DIY Network website as well.
Anytime you are starting a painting project, make sure you have all of your supplies before you begin. You don't want to get started and need to stop to run to the store... this is how unfinished projects happen! Also, make sure you prepare your surface so you give your paint job the best possible application. You can also consult your local hardware store for help. Paint pros there and at paint stores can assist you in choosing the correct products for your job.