After becoming familiar with the planets in their signs and houses, you're ready to look at how they relate to each other.
In astrology, the planets are said to aspect each other. This is their relationship, or the way they either create friction or harmony. Hidden in these relationships are more clues to understanding your unique set of "energies" and the interplay between the individual components.
I've outlined the Grand Trine in Fire in Harry's Chart because this would stand out to me in preparation for a reading. When planets "trine," they are of the same element. The red triangle is from Harry's Jupiter in Leo to Neptune in Sagittarius to his MC in Aries -- all fire signs.
The MC in astrology is the Medium Coeli, which means "middle of the sky" in Latin. The MC in a chart points to a career path, but in a wider sense to a person's destiny. Here, the MC in Aries points Harry toward being a pioneer and taking action even though he may be afraid.
The Grand Trine is just one of many aspects that can occur in a chart. For Harry, it is auspicious since it gives him a matrix of harmonized fire energy to fulfill his destiny.