Buy a Quality Paint Brush
I always recommend buying a quality brush, like a Purdee or Wooster. These can be purchased at any paint store and most home improvement stores. Quality brushes not only perform better but are easier to care for and will last a homeowner a lifetime.
Rinse Thoroughly
When you complete your project for the day, rinse your brush thoroughly under a stream of room temperature water. Work the paint out of the bristles by placing it in a bucket or empty paint can of clean water or press the bristles against the bottom of the sink as the water runs over it bending the bristles gently back and forth. Keep rinsing until there is no sign of paint in the bristles.
What to do About Dried Paint on Brush
If there is still dried paint deep in the brush you have two options. Your first option is to use a wire brush, which can be purchased wherever you purchased your brush.
While effective it is not recommended as it can damage the bristles. Brush the bristles of your paint brush with the wire brush working from the ferrule to the bottom in the same direction as the bristles. This loosens the paint at the base of the brush. Continue to hold under running water as you do this. A second, preferable way to deal with dried paint in your bristles is to soak the brush in Krud Kutter. This is a cleaning product that can be found at Lowes, or Home Depot and most paint stores. (You'll love it for all your cleaning projects.) It is very effective in removing dried paint from your brush when it is soaked over night. It also removes left over paint oils. Rinse thoroughly after soaking. (You can clean up paint spills with this product as well.)
Shake Out Excess Water
After your brush has been cleaned thoroughly tap it against your toe placing ferrule to tip of your shoe to shake out excess water. You can also use a brush spinner also available wherever you purchase your painting products. Once the excess water is removed place your brush back in the shuck (cardboard wrapper it came in) making sure the bristles lay smooth. Close the shuck and store. This will keep your brush in like new condition and will ensure ease of use in many future projects.