A few years ago our tomatoes were looking good, growing tall and healthy then it happened. The leaves started to look yellow and brown. Our tomatoes were being infected as well as the plant. We did research on it and found it was caused from the water on the leaves, more importantly bouncing off the ground and hitting the plants. At that time we were watering our garden like we water anything else, with the hose and spraying it with a wand or hooking it up to a water sprinkler.
The following year our watering method in the garden changed. It also made watering much easier. We chose to use a couple of soaker hoses instead. A soaker hose looks like a regular garden hose, however the hose is made of a different material and has several holes in it. This allows the water to come through the hose watering the garden with out getting the plants wet.
When it comes time to water, all we need to do is hook up our regular hose to the end of the soaker hose and turn on the water. It really is a good thing, as Martha Stewart would say.