Cost Approach to value is what it would cost to replace or reproduce the improvements as of the date of the appraisal, less the Physical Deterioration, the Functional Obsolescence and the Economic Obsolescence. The remainder is added to the Land Value. 
Comparison Approach to value makes use of other "bench mark" properties of similar size, quality and location that have been recently sold. A comparison is made to the subject property. 
Income Approach to value is of primary importance in ascertaining the value of income producing properties and has little weight in residential type properties. This approach provides an objective estimate of what a prudent investor would pay based upon the net income the property produces. 
Then, after thorough analysis of all general and specific data gathered from the market, a final estimate or opinion of value is correlated.