In astrology, electional astrology is the art of selecting an auspicious time for beginning something. There are a number of different ways to pick an auspicious time, but in general it involves evaluating the condition of the planets and their placement in your chart. Then you try to set up a chart that will be helpful in your endeavor, and minimize the influence of challenging planets. This is a very complex subject, and it takes years of practice to become skilled in this area.
The first thing that you do is determine what the planetary general significator of your topic is. For example, if you are choosing an auspicious date for marriage then you focus on Venus as the general significator of love and romance. You then evaluate the condition of that planet, and you want it to be dignified and free from affliction. You also want it to be applying to a benefic planet, or at least to a neutral one like Mercury.
Another consideration is the condition of the Moon and its lord. If these are poorly placed then the topic of your election will suffer in the long run. However, if these two planets are well-placed then the topic of your election will succeed from beginning to end.
Finally, you want to avoid having the fastest moving planet in your chart (the Moon for day charts and Saturn for night charts) making hard aspects to important placements in your chart. For instance, you want to avoid hard squares or oppositions from your malefic plant Mars or Saturn to the natal Ascendant ruler of the electional chart and to the house in your chart that corresponds to the topic of the election.