What is a good score for the SAT?

SAT scores are rather relative, since they truly depend on your aspirations, and more generally, what colleges, and for what major you are applying for.
If you desire to go to an Ivy League college such as Harvard, Brown, Yale, Princeton, Cornell, Dartmouth, your SAT score needs to be at least 2200 to have a fighting chance. Thus if you aspire to get into a top tier college, a good SAT score would be 2200+.

Now say you want to apply for a competitive major such as engineering or biology at a top college, then your SAT score needs to be higher, at least 2250.

Next if you want to go to a top public college like UC Berkeley (UCB), or UCLA, then you need an SAT score higher than 2050 to have a decent chance. Now say you want to get into UCLA or UCB for a competitive major like computer science, electrical engineering, mechanical engineering, biology, or chemistry, then you need a higher SAT score. 2100 will give you a higher than 30% chance of getting into these top public colleges, but a great SAT score for you would be higher than 2150, which will give you higher than 50% chances for the engineering and science fields.

Lastly if you want to get into the really competitive math/science/engineering schools like Caltech or MIT, then a good new SAT score for you would be anything above 2250. If you really want high chances, then you will need an SAT score of above 2300.