#1 - The most important tip of all time is water deeply so the bottom roots can drink. Too often people water many times a week but not deep enough.
#2 - Mulch holds moisture in the soil and keeps weeds under control. Be sure to keep 3-4" of shredded mulch on all flower beds.
#3 - Bugs love summer heat! Keep an eye out for chinch bugs ing the yard, aphids on flower beds, and mealy bugs under foliage.
#4 - Keep all plants well fed with a balanced fertilizer.