Before we delve into how to choose, first make sure any planters you are considering for use in your garden have drainage holes. We love using tin buckets in our gardens, but we do have to drill holes in the bottom to ensure proper drainage, we also add about 1-2 inches of gravel so that the holes do not get clogged with dirt.
First decide what types of plants you want in your garden. This will help you to decide what type of planters or containers you need. You will also need to know how big the root system of the plant will be, this will help to determine how wide and deep of a planter you will need.
How much water will the plant need? How much sun? Determine the positioning of your planter and the type of material used by these things. If you use a Terra cotta planter keep in mind that they can dry out quickly, unless you plan on watering frequently you will only want to have plants that need small amounts of water in Terra cotta planters. Synthetic or resin pots tend to retain moisture better and should be used for plants that need more water. Position your planters where they will get the optimal amount of sunshine for the plants that are in them. If you are planting more than one plant in a container then be sure that those two plants have similar needs.
If you live in an area where the climate tends to be colder then you will either want to put your planters up in storage each year when winter comes or you will want to invest in frost safe containers such as wood, stone, or cement.