Woah... whatever you do, DON'T guess the last 7!
The scoring algorithm is approximately such that for every question you get right, it gives you a harder question. If you get that right, it gives you an even harder question, etc. If you get one wrong, it gives you an easier question. And so on. The rationale is that eventually you'd converge to the level of difficulty that's as similar to your ability as possible. So, if you guessed most of the last SEVEN wrong, which is highly likely, you can imagine that the level of difficult just keeps dropping and you end up with a really low level question, which you might still get wrong. The computer will then think that THAT's your true ability, which is not the case. On the other hand, if your wrong answers are spread out, then they don't do much harm, because most of your answers would be correct, which keeps the difficulty up.
I hope I've explained it somewhat clearly. I don't think there's any particular question that's extremely important, but you should try not to get a string of questions wrong one after another, especially the final few questions, for the reasons mentioned above. The most important thing is to time yourself well so that you have time to read ALL questions, and even if you have to guess, make an educated guess.
