A planted container should look attractive immediately after or certainly within a few weeks of planting. Alpine troughs and 'arid gardens', by contrast, look best if the little mounding plants are placed with an inch or two in between. Try mulching the soil with inch of washed gravel, sand or small stones to give an alpine look. To determine when to water, just stick your finger into the soil. Always water thoroughly, at least until water runs out of the drain holes.
Water can run right through very dry soil without wetting it.
If you aren't sure, tip the container up to test that it has become much heavier with water. Count on more frequent watering for these. As a guideline, containers in sun require thorough watering twice a week minimum. Containers planted with succulents or drought-tolerant alpines require less frequent watering and can endure several weeks without the hose. Maintenance consists of removing faded flowers to promote re-bloom and pinching or shearing back plants to keep them looking tidy.