Summarize:

All lawns have an ideal grass height that promotes healthy growth. Depending on climate and geography, your ideal grass height is between 1/4 inch (0.635 cm) and 3 inches (7.62 cm). Talk to a landscaping expert or a professional at your local home and garden retailer to get an understanding of the type of grass you have and how high it should grow. Keep grass a little bit longer when in doubt. This will provide shade to your lawn, depriving potential weeds of sunlight. This will eliminate weed heads before they are allowed to mature or germinate in your lawn. Use a weed whacker or a trimmer on the weeds that grow at the edge of your lawn every time you mow. The cover will keep the ground cool and deprived of sunlight, discouraging the growth of new weeds.
Determine the ideal height of your grass. Mow your lawn as regularly as necessary to keep grass at its ideal height. Spread stones or mulch around your flower beds to prevent weeds from growing.