Very Cute Vintage I think Skye terrier planter.4 1/2'' T 7'' L A drainage hole in a planter is always ideal because it allows for any extra water to seep out of the bottom, which in turn helps keep the plant and its roots healthy.  If a planter doesn't have a drainage hole, we recommend treating your planter more like a cachepot by employing the double potting technique.  Place your plant into a smaller pot with drainage hole(s) and then place the pot inside of your decorative planter.  You can even line the bottom of the decorative planter with some gravel, which catches the extra water from the drainage holes and creates humidity which plants like. 

If you choose to plant directly into the planter, between watering wait until the soil is dry to the touch.  Then, try to moisten the soil from the top to the bottom.  The goal is maintaining a moisture balance to the soil so the plant isn't always needing water, which will lead to wilting, or watering too much which will asphyxiate then rot the roots, which will lead to the eventual death of the plant.  To that end, don't use a watering can.  Instead, use a spoon and add a spoonful or two of water and check the soil in a couple of hours.  If the soil is still dry to the touch, add a couple more spoonfuls and so on until the soil is lightly moist to the touch.  Or use fake plant lol