The GIGO Principle : This is a simple principle with a clear message and universal application - Garbage In - Garbage out!
Always try and enter any data in the form you want to see it printed out. For example, if you type in 'bkr' don't expect the computer to print out 'beaker'! Secondly be consistent in the way you enter your data. Using the same example, enter either 'bkr' or enter 'beaker'. Don't enter both because if you ask the computer to list all beakers, don't be surprised if it misses out the 'bkr'.