first off, i think many might agree with me in saying that PS is a joy compared to most DS problems.
If you are scoring in the 500's there are some basic DS tips that might help:
1- look at each statement separately, and think of the differences between sufficient vs. necessary. (i.e. a a sufficient condition of a rectangle is that it is a square but not vice versa... if someone is telling you it is a square you know without a doubt that it is a rectangle)
2-if you find a statement that works, don't let the other statement color your answer unnecessarily... really... this sounds simple... but it is common for people to find a statement that works, forget that the other statement is insufficient, but then see that the insufficient statement agrees in some way with the other statement and pick C or D. It still happens to me and I have gotten in the mid 600's on my latest practice CATs.
3-always think of all the possibilities within the boundaries given. I am still training myself to think like this... DO NOT FORGET that x might be a negative value, fraction, zero, etc... as this can make or break a DS question.