When choosing an electional chart it is always good to avoid periods where the topical house of the subject in question (for instance, the 9th for applying to college or the 4th for buying a home) has hard aspects from afflicted or debilitated planets. You also want easy aspects from the planetary general significator of that topical house in your natal chart.
The first approach

There are a few different ways of looking at electional astrology. The first approach relies heavily on traditional notions of what makes a planet strong or weak, dignified or debilitated, and auspicious or inauspicious. This means examining the ephemeris and identifying periods in the future when the planetary placements are especially favorable.

This can involve bonifying the benefics Jupiter and Venus, emphasizing the Moon and its significator, and mitigating the malefics Mars and Saturn, as much as possible within reason. This is the main way of ensuring that an electional chart will bode well for whatever endeavor you are trying to initiate.

The other important consideration is the topical house associated with the subject of the election. This is generally the house that relates most closely to what you are trying to begin, such as the 9th house for applying to university or the 4th house for buying a home. It is essential that the condition of this house and its planetary general significator be favorable.
The second approach

Electional astrology, like horary astrology, is all about lifting up the positive planets (Jupiter and Venus) and softening the challenging planets (Mars and Saturn), as much as possible within reason. This requires being comfortable with compromises since there is no perfect horoscope for any particular event.

Ideally all of the important planets in the electional chart are dignified (they’re either in their own signs or their exaltation) and they are strong, well placed and making positive aspects to other benefic planets. We also try to avoid having the challenging planets of the natal chart (Mars for day-chart people and Saturn for night-chart people) making hard aspects to any house or significators in the electional chart.

Another important principle is to avoid beginning new ventures while the Moon is void of course. Many electional texts advise us to wait until the Moon is in good alignment with the Sun before starting anything.
The third approach

There are a lot of rules to electional astrology, which can be confusing. In essence, the idea is to maximise the benefic planets and minimise their opposition from the malefics. It is also important to consider connections with the natal chart of anyone involved in the event, as well as the current solar return chart.

The first step is to find a general significator for the subject of the event, such as Venus in a strong and dignified condition for love or business. Then you want to make sure that the Moon is prominent in the chart, and in a good sign and house. Then you want to minimise the presence of the malefics by making sure that they are free from hard aspects from benefics and not angular.

Finally, you should also pay attention to sect (whether the chart is a day or night chart) and the condition of the South Node. This is because it is the natural ruler of the eclipses and therefore has an influence over the overall result of the chart.
The fourth approach

This approach to electional astrology is less focused on making sure the conditions are favourable, and more about trying to ensure that the symbolism of the planetary placements in the chart reflect what you are endeavouring to do. The important thing is to make sure that the general significator of your subject (usually Venus or Jupiter) is in good condition and ideally in its own or exalted sign. You should also avoid having the malefics (Mars for day-chart people, Saturn for night-chart people) in hard aspects to their corresponding house and/or natal placement.

Electional astrology is used to determine the best time for a wide range of undertakings, from major events like weddings and business incorporations, through to smaller but still important tasks such as signing contracts, listing a property or pressing the send button on an important email. It can be a very useful tool to have in your arsenal, although it does not guarantee success; only enhances the chances of success.