The first year, water will be required during prolonged dry spells—1" a week is the general norm. You can set a few cans in the border when watering to check the amount applied, or dig down a few inches 30 minutes after watering to see how deep the water has penetrated. A good 6" is ideal. Be sure to water deeply around and away from the center of the plant. You want the plant to be “reaching out” to find water. New gardeners are often surprised to find that what they considered a good soaking is only wetting the soil to a depth of an inch or so. If plants aren't watered deeply, they can turn out quite well but will be very shallow rooted. Subsequently, the plants can be hurt if a few days of watering are skipped and the top of the soil becomes dry. It's far better to strengthen your plants by deep watering when needed. This will make borders self-sufficient—exactly what perennial gardeners have in mind.
To keep weeds down, lightly scratch the soil as weeds are starting to show. This will destroy the few weeds that are visible as well as the multitudes that are just starting to break out of their seeds below. In order to germinate, seeds must be in the top of the soil layer, be in good contact with the soil, have ample moisture, and almost all have to be in the light. That's why once your new plants are up to size, the weed problem becomes minimal. As the plants mature and shade most of the ground, scratching the soil to minimize weeds can be more vigorous and watering less frequent.
For the most part, plants are insect and disease free. You shouldn't need any spraying unless a major invasion of sucking or chewing insects moves in from somewhere nearby. The damage should be easily apparent in plenty of time to use a general insecticide such as SEVIN or a general purpose spray before any real harm is done.