Annuals are generally susceptible to frost so you’ll want to wait until after the last spring frost date to plant them in the ground or to bring a pot full out to the porch. Your county extension should have dates on when the final frost date is for your area.
Planting on a cloudy day or in the evening protects plants from sun stress. It is wise to arrange the plants in the bed/pot before planting. Figure out the spacing between plants based on their mature size. Make sure they will have enough room to spread out and put on a show.
Most annuals are full sun plants and will put on their best show if they receive 6 hours a day of direct sunlight. There are annuals for shaded spots so select your plants with thought as to the location where they will be placed. Water dry plants prior to popping them out of their pots. Rootballs should be moist.
Remove plants from containers by slowly squeezing the pot as you turn it upside-down, holding the stem between your fingers gently cup the plant as it slides out. Stick your finger into the root ball and loosen it gently if the root ball is tightly packed. Make a hole large enough to hold the root ball plus a few inches of extra space. Place the plant in the hole roots first, gently push the soil in around the plant making sure there are no pockets of air. This works best when the soil is loose and loamy. Water after planting by soaking soil thoroughly.
For those growing annuals in containers, use a quality potting mix, never garden soil. For ease of care look for mixes that come with slow-release fertilizers and/or water retaining pellets. If the soil selected does not contain fertilizer annuals are heavy feeders so adding a time-release fertilizer will enhance the beauty of their performance.