Like @Lexicon said, looking up soil maps for your region and reading about the predominant types around you is a good start. You can also take samples of the soil from the areas you're planning to garden in and do a jar test to see what your prevailing mix is like - dig several test holes for each garden space and mix them to get a representative sample for each garden. Take some of the mixed soil for each garden area and put them in labeled jars with an equal amount of water and agitate the jars (after closing them). Let that water set for a while to allow the soil to fall out of solution and stratify - you'll be able to measure the layers of sand, loam, and clay to get a decent idea of what you're working with.

Knowing the composition of the parent material is good, but it won't tell you what minerals and nutrients are present. You may be able to find soil testing kits at a nearby garden center to do some tests yourself. Where we are, a nearby Agricultural College performs soil tests for a relatively low cost and allows us to select which tests we want done. Personally, I found a Haney soil test to be the most actionable out of the various mineral/nutrient/biological activity tests we've had done. Some labs will send treatment recommendations along with the results, with suggestions of soil amendments you can add to bring certain elements into the desired range (but the best way to amend and improve the soil is with plants!)

In addition to looking into your soil type, doing some research into the native plants of your area will provide many clues to what families of plants will do well for you. Check out some botany field guides or foraging guides from your local library, they'll often have information about the types of areas in which the plants can be found, as well as other species they'll grow alongside. There may be a native plant society around you (us plant nerds will talk your ear off) to make suggestions or share experiences as well as providing you opportunities to trade for plants. If you see someone working in their garden in your neighborhood: politely introduce yourself, compliment their plants, and ask them for advice for someone who just moved there and wants to garden*. If there is a local farmer's market, go there and ask folks what grows well and what plants to avoid.

*The latest new neighbor who did this to me got sent home with several dozen cuttings and a few more dozen starts