I can't speak for everyone but Cash Flows took me a while. One of the tips my professor in CPAExcel taught has really helped when it comes to determining cash flows from Operating, Investing or Financing. You take the normal accounting equation and strip out cash so you can solve for cash. Cash = Liabilities + Equity – Assets
Thus if accounts receivable increases you subtract it from cash from operating activities because you take the positive number and plug it into the asset. This really helped me with prepaids and deferrals because I would loose track of where they were in the basic account equation.