Data processing is required to make dataset appropriate for various classification algorithms. Here numerical data sets are converted as nominal datasets. Verbal ability score, quantitative score and MAT score has been converted as category data like ‘Low’, ‘Medium’ and ‘High’. The likelihood of placement may also be defined as two categories like ‘Yes’ and ‘No’.It is essential to have a suitable Data Mining tool for the purpose of carrying out Data Mining analysis of the data available. The software WEKA is suitable because it is open source. WEKA can efficiently work with limited data [11]. WEKA also provides convenient data preprocessing, cleaning and handling missing values. It takes data from excel file in Comma Separated Values (CSV) format, which is a very common application software to be used in each school / college for initial collection of data [12]. This software contains tools for a whole range of data mining tasks like Data pre-processing, Classification, Clustering, Association and Visualization.