Hint/Tip of the Day - Basics

The Basics:
Firstly, it's impossible to get very far without carefully maintaining a list of 'possible values' or candidates for each blank cell. Doing this by hand is laborious and prone to error, and often detracts from the fun of solving these puzzles. Fortunately, programs like Simple Sudoku will do this for you, while leaving you with the fun of applying logic to solve each puzzle.

If you don't have a program to help - systematically analyse at each blank cell. Start with the assumption it can have any digit (or value) between 1 and 9, and then remove all values which have already been assigned to other cells in its respective row, column and 3x3 box. This leaves each blank cell with a list of candidates.