All plant-life depends on the availability of water and the best source of water is rain. Rainfall patterns are always determined locally using available weather records and these are almost always available from your local meteorological service. You will of course be aware whether your area has lots of rain or lots of drought and perhaps everything in between. However if you are starting out as a gardener a little bit of research will help you to decide what you can and can’t do.
Local weather patterns may affect the selection of plants that you use in your garden, as well as the layout and the theme. It is important to create a garden that is appropriate to the climatic area where you live and you shouldn’t try for instance to create an extensive green lawn and herbaceous borders in areas of little or no rainfall.
Soil conditions depend to a degree on weather conditions and on the amount of available rainfall. They are however in the first instance determined by local conditions and by what makes up the structure of the earths surface in your area. If your locality has a thin layer of topsoil over deep clays then your soil conditions are likely to be wet. On the other hand if you have deep, humus rich soil over free draining subsoil your soil will be most likely free draining and fertile. Take a little bit of time to have a look at your soil, and in particular how it handles water. Does the water pass through freely allowing air to circulate in the soil or does it hold water? Do you live in a fertile river river area or near an arid desert area?
Try to be true to your local soil conditions, as working with them will be far more rewarding than trying to drastically change them. You can of course easily make small changes, like adding humus to sandy soil to increase water retention and fertility. On balance though it is best to have a look around at what tends to grow naturally in you local area and to mimic that in deciiding how to set out your new garden plan.
For an excellent example of a garden that made wonderful use of its location do an online search for images of Derek Jarmans garden in Dungeness in Kent. This is well documented in his book, Derek Jarmans Garden.