For a lower skill player, I would recommend just hitting the 9 to the opposite long rail, either above or below the side, and sending the cue ball back to the lower long rail. Unless you leave the 9 ball hanging in front of the side, you are leaving a tough bank or cut for your opponent.
Myself, I would either cut it in (depending on exact position) or would try a variation of the 4 rail shot mentioned. I would bank the 9 ball toward the 1st diamond or so on the top long rail. It has a chance to go 3 rails in the bottom side, and if not it will often end up close to where it started in the middle of the end rail. Meanwhile the cue ball with some low right will travel toward the opposite end rail. This takes a bit of practice to get the hit/speed right, but it's almost always effective unless you hit the point of the side pocket, and even then with good cue ball control you still can often leave a long shot.
Scott