According to our Gooseberry Patch "For Bees and Me Cookbook", Candy Hannigan explains that there is no need to fill the entire barrel with costly (and heavy) potting soil. After drilling holes in the bottom of the pot, fill 1/2 to 1/3 with package peanuts, cover with landscaping cloth and then fill the pot with potting soil and plant your annuals.
Nancie Gensler reminds us that when purchasing plants, resist the temptation to buy the larger one in full bloom. These plants have already reached their peak. Instead, pick the youngest plants; they will have a much longer flowering season than the plants already in full bloom. At least once a week, remove dead and faded blooms from your plants and they will continue to produce more blooms. Your garden also looks neater when you "deadhead."