There is an entire body and many books of advice that could go into advice to someone who wants to start keeping a garden. So for someone starting off this can be quite a daunting task. I do recommend reading up a few good books before starting off gardening and starting off on a smaller scale and then making baby steps to keeping your garden.
The first and foremost you have to get started off with the garden. As earlier stated you can start off with a square foot and then expand if that’s how you’re inclined. Starting off and being there to do the work is the most important part of having a garden.
To have a great garden you will have to work hard at the soil in addition to the plants. So mulch or compost needs to be fed to the soil regularly. If the soil is healthy then it has the right proportion of air, water, nutrients et al.
It is not hard to make your own compost from what you is going to waste anyway. You can use this compost in your garden to improve the soil structure and texture. That makes a pretty big win-win!
Finally, try to keep plants grouped together as tightly as possible as in companion planting so that they can promote growth and allow for maximum utilization of resources.