Try to know as many equations as you can but definitely anything related to thermodynamics (very high yield), work/energy, acids/bases, waves/optics, and electricity/magnetism. Also, make sure you know your basic math ie dimensional analysis, logarithms/exponents, trigonometry, etc. As you may have noticed it's a matter of luck but you don't want to skip memorizing a few basic equations and be slapped with a calculation-filled C/P section.
I would also strongly recommend first understanding the implications of the equations wrt the relationships between the variables before memorizing them. If you don't know how to apply an equation or how to use a relationship conceptually there's no point knowing it.