As a beginner, its seems like there's a lot to learn.  Yet it's not nearly as difficult as it looks.  Learning by imitation is a good way to start.  If you have a community garden or your neighbor has a healthy, productive garden, there is no harm in looking over the fence and copying :)  And, don't be shy about asking for advice; gardeners notoriously like to talk about their prowess.  

My theory, is to strategize, but don't over think it.  Gardening is, after all, just the cycle of life in action.  And when it comes to container gardening, there's not much to know.  Just be observant.  The plants will tell you when they want to be watered, have had too much water, need more sun or are getting scorched.  Your first time will be a bit reactionary, but then for the coming years, you will learn from your successes and mistakes.

Pots and containers

Trays, biodegradable tubes, and seed pots are all used at the start of a plant's life (at least most plants).  They are for sowing and germinating seeds, planting cuttings and growing seedlings.  Then, when they get to a certain size, the plants often move on to a new home.  Yet not all transfer to a home in the ground.  For those that will remain in a container of some sort, there is one inviolable rule- there must be a hole or holes in the bottom of the container to allow drainage and prevent water logging or molding.

When choosing the container, there are many different options and they vary greatly in price.  Choose a container based on price, esthetics, durability, and keeping the plant in mind.  Choose a container that your veggie can grow into.  For example some plants that will be top heavy, require a heavier container to ensure that they do not tip.  There are many options available.  My personal favorite choice is a modern looking container made of recycled materials (such as tires) that has a "self-watering" insert. Just note that this "self-watering" insert doesn't actually water the plant, it just lifts it off of the bottom of the container and catches the the excess water there, which keeps the plant moist until it has evaporated.  These containers not only look good, they are durable and the recycled tires prevent pests- great multi-tackers!

Soil and compost

I love having my own composter.  We take all of our plant based veggie scraps (no animal product!), egg shells (yes I know what I just said, but this and lobster shells are the only exception), coffee grounds, dead plant clippings from the garden, and grass clippings and put them into our rotating composter.  We add an organic starter twice a year, a touch of water to make sure it stays moist, and then spin regularly.  It bakes in the sun, although ours is hidden behind a tree so we don't have to look at it, yet amazingly it doesn't smell or attract animals.  We fill it all year and by the time we get around to the growing season it is perfect- crumbly, moist (not wet or slimy) and smells like dirt.  Just remember to NEVER, NEVER add weeds or diseased plants to your composter- otherwise you are simply making a weed starter!  

If you don't have the time, energy, space, etc for a composter, then there are several other options depending on how much you need and want to spend.  Organic compost, manure or organic gardening/potting soil can often be delivered or purchased in bags at your local nursery or home goods store.  For an existing garden or for pots you probably won't need much- but the cost benefit of composting your own is amazing.  For newer gardens, order more than you expect that you will need and "dig it in" then let it settle for a few weeks before planting as it will compact.  And, as with food, read the labels.  If the package includes chemicals you wouldn't want to touch your food, you don't want it in the compost such as industrial chemicals, herbicides, pesticides and fertilizers.

Fertilizers

The last prep step is fertilizing.  If you used your own organic compost, great you are done!  If not add an organic, soluble fertilizer to your garden prior to doing any planting.  Sprinkle the fertilizer onto the surface, gently rake it in and then water.  This preparatory fertilizing is called a base-dressing and can be followed up with a top-dressing after your have sown your seeds or planted your seedlings if you so choose. And that's it, you are prepped.

Now, you are ready to plant your garden!