Use a pencil with a clean eraser as a beginner.
Start with easy puzzles. If you can do it in less than 15 minutes, move on
to the next higher level.
Seek the easy answers first. It is best to get several cells filled in.
Focus on the regions with the most numbers filled in, rather than the open
regions.
Also focus on the rows and columns with the most numbers filled in.
Take a break and start fresh later if you are not making any progress.
Never guess in Sudoku. You may get more problems.
You may mark the cells you fill in with a pencil so that you'll know what to
erase if you make a mistake later on and find it impossible to move on.
