I spot at the foul line and the boards at the arrows. Some bowlers spot further down the lane as where their breakpoint is.
My method of targeting is called 'line bowling' as opposed to 'spot bowling'. Line bowling is the next step up from spot bowling and uses two spots (in my case) as opposed to using a single spot.
The problem with using only one spot is that you can hit your spot and still miss your target at the pins. Recalling your high school geometry "an infinite number of lines can be drawn through a single point". Therefore if I roll the ball over my spot at the wrong angle, I will miss my target.
rolling the ball over your spot at the wrong angle can be eliminated if you line bowl. Again referring to high school geometry, "two points determine a straight line". So if I can roll the ball over a spot at the foul line (or the 6 ft dots if there are any) and the boards at the arrows I have a good chance of hitting my target at the pins while taking into consideration ball speed and lane conditions.
In all cases, the other spot to be factored into the equation is where to stand on the approach when using a specific target line.
Where you stand is being able to walk in a parallel path 5 boards from the line that your ball is taking.
All of the above requires experimentation with regards to establishing
Target Lines for specific situations.
During my stance I align my armswing with the line that is determined by the spot at the foul line and the target board at the arrows. Once I take my first step I don't look at the spot at the foul line but try and keep my armswing in line with the spot at the foul line so that I release the ball over that spot and out to the target board at the arrows.
To help keep everything moving in the right direction, my followthrough is toward where I think the breakpoint might be.