My main goal in my pre-MTC study is to be prepared to give all five missionary lessons by the time I arrive in Peru.
My secondary goal in my pre-MTC study is to improve my Spanish grammar and vocabulary. To achieve that goal, I'm studying The Ultimate Spanish Review and Practice by Gordon and Stillman. It's the recommended study guide for returned missions to help them brush up on (and improve) their Spanish. It's a great book. Even though I've been studying Spanish on and off over the past 10 years, I still need to shore up a few finer points of Spanish grammar.