Choose a planting pot made of terra cotta, wood, plastic, metal or artificial materials. Find a style and color that pleases your eye and matches the style of your surroundings. Go with the largest container that will fit the display spot. Larger planters won't dry out as quickly, and they have more room for healthy root growth.
Consider the spot you will place your planter. Does it receive full sun, full shade or something in between? You will need to pick flowers that do well in that exposure.
Determine how many plants you will need to fill the pot. The most spectacular planters have plants nearly touching each other. While you will need to consider mature plant size, as a rule, plants are spaced much more closely in a pot than they would be in the ground. For a planter filled with annual flowers, you can plant so that the root balls are nearly touching.
Choose plants in three categories: taller plants to make a statement, creeping plants to hang over the edge and filler plants to go in between. The best looking planters have these three elements, often called "thriller, spiller and filler."
Pick plants that have similar growing requirements. Color choice and foliage appearance are up to your own taste, but combine plants that please your eye.
Purchase potting soil specifically designed for planters. Don't use dirt from your garden, as this will harden in a pot and kill your plants.
Fill container with potting soil up to 4 inches below the pot lip. Work some granular, slow-release fertilizer into the soil.
Position the plants in the pot. Put the taller plants in the middle or toward the back. The fillers should go around the middle and the spillers at the edge of the container. Have root balls close to each other, almost touching.
Fill in the rest of the way with potting soil, leaving 1 inch at the top for watering. Be certain to fill in around root balls, leaving no gaps or open spaces without soil.
Water very gently, letting soil settle and washing dirt from leaves and foliage. If soil settles too much, add a small amount of soil to fill in the gap.