If you have a bad back or trouble lifting,  the large clay pots will be too heavy, so go for the plastic!  It should be at least 8 inches deep and have drainage holes in the bottom .Window boxes are nice on a rail or balcony.

A bag of "potting soil" It is lighter weight and made for pots, I like the kind with time relised fertilizer and moisure retention crystles. Or buy some fertizer. Don't use regular earth or soil.

A watering  can.

Things to keep in mind when you choose your plants are how much sun the plant needs. Make sure you buy plants that are suited for the sun exposure of the location you are planning on putting them in.

Look at the little tag in the plant and see how much sun it needs and how tall it grows.  Put the same sun types in the smame pot.

Some plants need 6-8 hours of sun, some need shade, and some are ok with a little of both.

Some of my first outside plants were containers filled with pansies.  Simple yet very pretty.  One pot was all deep purple, the other bright yellow.  They did well once I realized the bright sun I had them in was killing them, and I moved them to the  cooler shady part of the yard and they sprang back to life!

Some easy plants for sun are petunias, geraniums, lavender, daisies, allysium, dusty miller,

Some easy plants for shade are impatients, lobilia,  pansies.

 Or mix  a variety of plants, some  trailing, some tall or spikey, and some of the full type  if you want to be artistic.  But even a pot or window box filled with all one kind is nice.  Choose a color scheme or color combinations that complement the place you are putting it. 

 Fill your  container or window box about half full with the potting mix,(add water to moisten the mix if it's dry).

 Plan to set plants about 2 to 5 inches apart in the container, remembering they are going to grow and expand. Slip plants out of their pots without pulling on the stems. Fill the spaces between plants with soil mix, tapping gently.  Water thoroughly to settle the soil.

 Container plants require frequent watering, often daily in hot, dry weather.  Morning is the best time, so the sun can dry off any water splashed on the leaves and prevent mildew. Also the plant won't get parched in the hot sun waiting all day for a drink  Soak the soil completely at each watering.  Trim dead flowers and stragglers, they usually get healthier after a trim..