Drainage! Drainage! Drainage!
We need to start using pots with drainage holes! Drainage is so important when it comes to watering your plant. If your planter doesn't have drainage there is no airflow, the water sits in the pot for too long, or pools at the bottom of the planter. This is just a recipe for root rot.
If your planter doesn't have drainage you can either drill a hole in the planter or use a nursery pot (that has drainage) and place it inside of the planter that doesn't have drainage (Featured above).
Side Note: I don't know who started this, but don't put rocks at the bottom of your planter. When you water, it will pool at the bottom of the container. Eventually, your roots will grow around the rocks and will sit in that pool of water.