Inland Northwest, High Desert
Keep Soil Damp, Not Wet
Good potting soil should come out of the bag evenly moist. If it isn't, add water and stir until it holds the shape of your hand when you squeeze it. Once peat moss -- the main component in most soils -- dries out, it is difficult to re-wet. Better to start out damp.
Water Before Transplanting
Water every plant you bring home thoroughly before you transplant it. If it is a large pot, it's better to pour water through until it drains out the bottom two or three times. Research shows that prewatered transplants are five times more likely to survive than those that were planted dry.
Don't Cover Drainage Holes
You don't need to put rocks or pot shards over the drainage holes in pots. They will probably just block the holes so excess water can't escape and air can't reach the roots. Soil will stop falling out the holes in the next watering or so.
Let Your Pots Come Up For Air
Roots need air. Even if a pot has drainage holes, if you set the pot on a flat surface, or even in a saucer, much of the air is cut off. Instead, use some of the new, cute, pot feet you'll find at the garden center. Pot feet raise the whole container up an inch or more, allowing air and water to pass freely. And because it dries out between waterings, your deck won't stain.
Help Cascading Plants Do Their Job
When you put plants at the edge of a planter, hoping they'll climb over the side and trail down some day, help them. Set them in on their sides. That way, they're already hanging over the side and look great.