For sentence equivalence, I know of 2 strategies.
1. If you have a good vocabulary, then try to find the pairs of synonyms before diving into the question. This shouldn't take but more than 10 seconds. Usually, there are two pairs of synonyms and two answer choice irrelevant to the question. Next read the question, find the contextual clues, and pick your pair of synonyms. The context clues are pretty obvious. Most times they define the blank, relate the blank to some idea, or use shifts to oppose the aforementioned first and second point.
2. Do #1 but in reverse.
Fill in the blank (Sentence completion?)
1. You will see 6 of these on the test of increasing order.
2. Context clues are key - The blank is either defined or part of some cause and effect to a general idea of the sentence. The blank may or may not be reversed by "shifts" in the sentence.
3. Vocabulary in context is key to these questions.
4. So is the understanding of the general idea the question is conveying.
5. For 2-3 blank questions, I usually find the 2nd or 3rd is the easiest to tackle. Sometimes other blanks can be solved separately of one another, but usually with the harder questions I find the "easiest" blank telltales the others.