Healthy soil equals a healthy garden. Before you begin to add amendments, it is helpful to know what kind of soil you have. Clay soils need different things from a sandy soil.
A basic way to test your soil type by feel. The University of New Mexico has simplified the procedure. You need a small handful of soil, and just enough water to break down the aggregates, to form a simplified soil putty. Then, answer the questions in the graphic below.
Types of Soil
Individual grains can be seen and felt. The soil falls apart when squeezed when dry, and will hold its shape when you release pressure, but crumbles when you touch it again.
Sandy soil, with enough loam to give it some structure. The individual sand grains can be seen and felt. It has the same properties as sandy soil when it is dry, but when it is wet it holds its shape when touched.
Even amounts of sand and silt, and a good amount of clay. It crumbles when it is dry with a gritty but smooth feel. It holds its shape when it is squeezed dry, and when wet it holds its shape well.
Contains moderate sand, small amount of clay, and a good quantity of silt. It holds its shape when dry or wet. Dirt clods can be broken up easily, and feels soft and powdery when pulverized. When it is wet, a ball of soil will have a crumbly texture.
The texture is fine, and breaks into clods when dry. When a ball of wet dirt is rubbed between the fingers, it breaks easily, but the moist dirt holds its shape when squeezed and can take considerable handling.
This is a fine textured soil that forms very hard clods when dry, and is sticky when wet.
Graphic of Informal Instructions for Estimating Soil Texture by Feel courtesy New Mexico State University.