Although physical features are important, the most critical feature of your appearance is verbal behavior. The fluency with which you use language is an almost fool-proof clue to your educational level. The classic way to improve verbal fluency was to study Latin because it was believed that "formal discipline" would transfer to English. Although that doctrine has never been disproved, it is probably more efficient to work directly on English. My hypothesis is that all of the verbal skills--listening, reading, thinking, writing, speaking--are inter-related so that effort spent improving one tends to improve them all.
Because world knowledge is non-verbal, college learning is not as much learning words as it is learning from words. That is to say, the words used in a college course represent thoughts or ideas, and your job is to learn those thoughts or ideas from the words spoken in lecture or written in the text. Words convey information, but you have to "process" the words in order to understand the information.
Processing verbal information is analogous to "digesting" words. Instead of merely mimicking the words verbatim (maintenance rehearsal), you need to interpret the signals as meaningful units (words), chunk the words into larger units (phrases, clauses), parse the chunks into parts of speech (e.g., subject, predicate), code verbal information into nonverbal ideas and then associate the new ideas with old ideas that are already in memory. Elaborative rehearsal requires dividing attention between receiving and processing the information. This ability to time-share one's limited attentional capacity is learnable.
If the new information contains familiar ideas, these are processed automatically and hence require very little of your limited processing capacity. This is the reason why, in general, the more you already know, the easier it is to learn. The exception to this rule is when the new information is incongruous with your existing knowledge. In that case, it is not only more difficult to learn, but you may distort the new information so as to make it fit better with your old knowledge.
Processing verbal information is the input side of verbal fluency. The output side (speaking and writing) is equally important. Your mind would be a black hole if it could only absorb knowledge and not express it. To be sure that you have really processed an idea, rather than simply memorized it, professors usually want you to "put it in your own words." To evaluate your skill at paraphrasing ideas, you should do the exercises in Appendix E.
In putting ideas into your own words, you will be judged not only by what you say but also by the way you say it. Educated people pay attention to their own grammar and hence will notice yours. You should review the points on grammar made in Appendix F. Learning to recognize and avoid grammatical errors is an important aspect of verbal fluency.