The worst thing people can do is vote strategically. All that does is ensure you're voting for someone you don't actually want, and stops any smaller party ever getting anywhere. Look at the last election: the LibDems did outstandingly well, which they never would've done had people voted tactically. Yes we ended up with a coalition government, but that has worked out so much better than anyone (myself included) thought it would. Two parties, with pretty much nothing in common, have worked together with minimum fuss.
That's exactly what politics should be, people working together for the greater good.