Often a board has what is considered a top, bottom, left, and right side, whether it is due to how the designer saw it in the layout program, or how the silkscreen text is oriented.
It is easier to read the resistor values later if you orient them all so they read correctly from left to right when the board is oriented top up, or when the board is rotated 90 degrees (rotated either direction, take your pick) for resistors oriented that direction. Similarly, on through-hole resistors that have printed text instead of bands, bend the leads so that text is facing straight up away from the board for easiest reading.