FWIW, YES! Memorize the solubility rules, but be aware that you get slightly different versions based on whether you are reading Kaplan, TPR, or etc. So, it's important to remember that the solubility rules are not a binary thing. It's a spectrum of solubilities, and where one person defines "insoluble" may not be the same as where another person defines "insoluble". You should definitely know the basic rules, and if you have time, learn exactly why: i.e. "A phosphate of X, Y, Z is soluble/insoluble because ____"