It's absolutely crucial to remember which way round cathodes and anodes are. One is the positive terminal, and the other's the negative one. And one is (normally) black, and the other is red (most of the time).
Fortunately, there's a simple and foolproof method! You see, cats (well, some of them) are black. Some ants are red (well, OK, so you see more black ants, but let's forget about them for now). (If in doubt, remember that you don't get red cats (well, I've never seen any (yet)).)
Now, cats are black, and black is the colour of wicked witches, the devil, and, er, other negative things. Therefore, cathodes must be negative. And so anodes must be positive. (Forget all about the fact that the devil is sometimes red, not black. And that hell is a fiery red place. And that that red is the colour of temptation. And the colour of blood and war. All of which are pretty negative concepts. And don't even start to reason that black is represented by 0x000000 (i.e. 0) in standard 24-bit RGB notation, a value which is by definition non-negative. (Of course by that reasoning, however, you could say that, relatively, black was indeed more negative than any hue of red.))
It may be useful to remember that red indicates the port (left) side, and that green indicates the starboard (right) side. On a graph, the left side (assuming you're looking at it the right way round) is normally negative, and the right side positive. (OK, so the bottom is negative and the top is positive too. But never mind that right now.) ... Oh no! That's all the wrong way round again. On second thoughts, it really isn't remotely useful to even think about seafaring right now.
Other methods of recalling the positivity or negativity of cathodes and anodes which also completely fail include counting the number of letters (cathode has more letters than anode, but is more negative) and comparing the alphabetic position of the first letter (c is a positive increment from a, not a negative one). I'm still working on a revolutionary technique for remembering them based on which of Henry VIII's wives the words are most connected to and which fates the wives suffered.
Remember, though, that this only applies to cathodes and anodes, not cations and anions. Cations are attracted to the cathode, and are therefore positive. Anions are attracted to the anode, and are therefore most certainly negative. At least, I think all that's correct. Easy, isn't it?