Along axes:
Press W to walk forward
Press A to walk left
Press D to walk right
Press S to walk back

Combinations:
Press W+A to walk diagonally (forward+left)
Press W+D to walk diagonally (forward+right)
Press S+A to walk diagonally (back+left)
Press S+D to walk diagonally (back+right)
Press A+D to stop moving sideways
Press W+S to stop moving forward/backwords

I hope it helps