Since we have moved to Texas it has been a learning experience getting used to having 2-3 growing seasons. We will start putting seeds in the ground this week (1st week of Feb), most of what we plant now we will plant again later in the summer. Then there are a lot of great things we can plant over the summer that take the heat really well and keep our garden beds full and beautiful during a received "off time". While we are planting now we are still harvesting; kohlrabi, broccoli, carrots, beets, turnips, rutabagas, fresh herbs (cilantro, parsley and dill) and snow peas. We will have a much more productive winter next year.
One thing that has really helped us know when to plant everything is a chart a local master gardener compiled, that lists what to plant and when. It also lists what to plant in the fall season too. This is a good guide and give a point for reference. We put the dates on our calendar so we can see what we need to plant each week. While this is a good guide it is not a set in stone time table. Planting guides are based upon the average last (or first) frost dates for your area. These frost dates can be different from town to town.
I have found a great site where you can find a planting guide based on your climate zone (searchable on the site). It is a good start and a good basic guide. It breaks it up by combining two climate zones... 5,6 7,8. So it's only a general guide. Also look up your local extension office. Gardening is a learn as you go process, you learn from mistakes... and mistakes are okay.
The first step is to look up your average last frost date. There are many places online to do this, I have used Zipdatamaps.com search by zip code. Also a lot of city websites will list this information too.
Once you know your last frost date you can begin to examine your seeds to see what needs to be started before and what can be planted after. Often is makes sense to plant the same seeds over the course of several weeks. So that if a sudden cold snap hit your haven't planted 100% of your seeds, you can also use row covers and other passive methods. By spreading out your planting you also start what is called succession planting, this will extend your harvest season, as each type of plant will produce on a slightly delayed schedule.