What are the main checkpoints to look out for when attempting an abstract reasoning question?

You need to look at the numerical side - numbers of objects, numbers of corners, numbers of sides to the shapes, the number of shapes + to the number of corners, the number of lines and contained shapes etc. at the colour side - whether they are all a certain colour or certain shapes are certain colours or the number of coloured vs blank shapes etc. Other things you can look at are the angle of rotation of shapes, the angle a which lines are tilted, how many times the lines intersect (and how many compartments this makes), whether all the shapes are in one corner of the square, whether the order of the lined up shapes changes or stays the same etc. With practice, this should become easier!