Newbies are often afraid or insulted to use "handicap" pieces, but the few free pieces given to a lower-rank player are actually quite effective at adjusting the balance with unevenly ranked players. It's not a huge advantage and doesn't fundamentally change the play of the game.
Using different sizes of board is also neat. I'm very fond of a short game using only a 9x9 board. Plays a lot faster, but trades strategy for a more tactical game.
I take the square root of the negative trolley, then use my imaginary streetcar to establish a complex track so I can start killing in an additional dimension.