Rain Reigns
The prospect of spending two or more hours watering the yard in between rain storms doesn't really excite me.  I usually start out by filling (cleaned and emptied) milk jugs with water from the rain barrel (conveniently poised under the gutter drain, but inconveniently having the spout so low that it's difficult/impossible to fill the jug to the top-unless you are some type of Houdini) then resort to the hose when the barrel runs dry.

Several sources I've read recommend only deep watering.  That is, try to get the ground completely soaked. If you cut time corners (like using a sprinkler) you are not helping your plants; the water may not penetrate the ground enough (unless the sprinkler runs a very long time).  Also, if you water during the hottest hours of the day you may lose a lot of moisture to evaporation.  A couple of other tips: try not to wet the leaves of your plants while watering, diseases (like powdery mildew) may spread faster or appear, and if you water in late evening you may attract insects to your plant.

As a general rule of thumb, always check on recently planted trees, shrubs, perennials, and annuals on a frequent basis as their watering needs are far more.  After two years or so (depending upon how dry the summers are) trees and shrubs are fine without extra watering, they have sent out their water roots and can help themselves.   If you go for days without significant rain, check the color of the soil.  Is the top layer the same color as an inch beneath?  If so, go for a deep soaking or your plants may wither up and blow away.  I have been known to push the time between waterings as I let the local meteorologist be my guide (and often they are wrong).  If I see rain in the forecast I will put off watering until the next day.  I do not recommend this method, however, as in Maine, the weather can be highly unpredictable (a forecast of rain will often turn to just cloudy for days on end).

"Jack's Rain Barrel"

If you choose to use a hose for watering, a couple of tips.  Try to get a submeter for just your outside water supply (otherwise you end up paying sewer charges along with the water charges in your monthly bill, and, in Portland, sewer can make up two thirds of your utility bill).  If you want to use a rain barrel, check out your local Public Services Department to see if they offer one (usually in Spring) at a discount.  I purchased mine from the Portland Water District a few years ago and it's a nice terra cotta color so it blends well (see in the photo to the right that it is also strategically placed to capture water from the gutter and to not impede the overall look of the garden).

In viewing the recent rain barrel offerings at the City's Public Services Department, I'm glad I have the other one, the new one (pictured below) looks to me like a giant cup of Starbucks and I'd be craving (fancy) coffee if I had to look at it every day (and as coffee grounds from my old fashioned coffee maker make for excellent top dressing on my acid loving plants, I'd hate to waste resources and money on a giant cup of coffee that I don't really need-plus I'd like to sleep sometime in the near future).