Archeology excavation methodology follows a standard procedure that is contained in many protocols, some of which are public and others which are private and proprietary. It is important at the outset to determine if you are dealing with partially decomposed tissue or if you are only dealing with skeletal artifacts. If the former, then you are treading on the area known as bioarcheology, a specialty field with a rich literature base.
There are few substitutes for laboratory work in this field, and the experience you'll need can only probably be obtained from working a "body farm" that a professor has set up somewhere. To study decomposition, the typical "body farm" will use a 50-pound pig, the next best thing to a human corpse, and the processes of decomposition are similar.
In a very wet environment (like a rain forest), a body will be stripped to the bone in about 18 days, and in a very arid environment (like a desert), there may still be flesh on the bones after a year.
Some standard procedures to all forensic archeological projects
Clarify the stratigraphy of a site. Soils are normally subdivided into naturally-occurring stratigraphic layers (or strata) that are distinguished by their color, texture, grain size, and material components (silt, clay, and sand). The uppermost layer (topsoil) generally is dark because it contains large amounts of organic material from decomposed vegetation. The deeper layers (subsoil) are generally lighter in color, contain less organic matter, and contain more clay and gravels. The process of digging a hole or clearing a 40' x 40' area disturbs the natural stratigraphy, resulting in a mixing of soil from different strata. The archeologist determines the original layering and reconstructs the sequence of events that disturbed it. Specific disturbances such as burial shafts, animal tunnels, trash pits, campfires, drainage ditches, house foundations, uprooted trees, etc., are called features. The archeologist generally removes a single stratigraphic layer or feature at a time before proceeding to the next deeper one. This will ensure that evidence from different layers or features will not be accidentally mixed. The archeologist may further subdivide a particular layer into levels of arbitrary but standardized thickness (usually 5 or 10 cm). Remember that the soil composition in the area may have been modified by fluids that have seeped from the body, this being particularly important if you are dealing with skeletal remains.
Recover all evidence. Small bones and unusual items (such as insect puparia) are easily missed by the untrained eye even when clean, and adhering dirt and debris makes recovery even more difficult. If small evidence is expected, soil and debris is usually screened through 1/4" or finer wire mesh. We commonly employ large rocking screens, hand-held screens, and geological sieves. We use the term evidence loosely to apply to all artifacts and human remains recovered at the scene but also to include miscellaneous items such as footprints, tool-marks, plant roots, insects, graveshaft features, and stratigraphic, locational, or contextual information. Artifacts refers specifically to physical objects that have been used and/or manipulated by humans, including but not limited to jewelry, coins, clothing, weapons, projectiles, and trash. Remains refers to human bones and soft tissues, including teeth, hair, and nails.
Document the exact proenience of all evidence. Provenience refers to the coordinate location of an item in 3-dimensional space, reflecting its latitude (north-south location), longitude (east-west location), and vertical position (depth), as measured in meters (m) and centimeters (cm). Without this control it may not be possible to be sure exactly how or if an item is truly associated with the remains in question. Archeologists use the metric system to record things because it is much easier to work with than the standard English system of measurement.
Determine whether evidence is "in situ." An item that is still in the position in which it was originally deposited is said to be in situ. The forces that move items out of position (e.g., humans, animals, water) must be explained and understood.
Limit postmortem damage to the remains. Uncontrolled removal of the remains with shovels invariably damages fragile bones and evidence. The identification of perimortem trauma is made more secure by controlled archeological excavation using small tools, such as trowels, spoons, and wooden picks.