- Outer planets (Uranus, Neptune, Pluto) spend almost half the year retrograde, and they don't rule zodiacal signs, so for most purposes, one can ignore the retrograde cycles. The one exception to this is if the planet changes direction within a degree or so of one of your personal points in a chart (Ascendant, Midheaven, Sun, Moon, for example).
- Jupiter and Saturn each spend about 4 months retrograde in a given year. So unless you have a big focus of planets in their signs (Sagittarius, Pisces, Capricorn, Aquarius, Cancer & Libra [these last two are the exaltation signs of Jupiter and Saturn]) don't worry too much about these. The most important thing here is to see what house it's going through in your chart and accept that there may be some slow-downs and reversals in those areas.
- Mars will spend 2-3 months retrograde, on average, but it only happens about every 2 years. See above for Jupiter and Saturn for how to deal with this. Mars signs are Scorpio, Aries and Capricorn (exaltation).
- Venus goes retrograde about every 18 months, for about 6 weeks at a time. Venus signs are Taurus, Libra, and Pisces (exaltation). Venus also rules relationships in general, love, lust, and to a certain extent, fun. So this has the potential to affect everyone in these areas, as well as those who are heavily Venus-ruled.
- Mercury goes retrograde on average 3 times a year for about 3 weeks each time. Mercury-ruled signs are Gemini and Virgo, so if you have a lot of this in your chart, it may affect you personally. Also, Mercury is the natural ruler of communications, thinking, writing, and Merchants. So these things, as well as mechanical items, are usually affected more directly for everyone.
A retrograde planet is far more likely to affect someone if it goes retrograde, or turns direct, at or near the position of a planet in your own natal chart. A Mercury retrograde passing over one's Ascendant, for example, will be more significant than one that is buried in the 8th house, with no aspects to anything else in the chart.
Another time that one might be affected specifically by these retrograde cycles is if one is in a planetary period that corresponds to that retrograde planet. For example, if you are in a Jupiter period, and Jupiter goes retrograde, this may affect you. I'll post more on these periods at a later date under the topic "Firdaria", so watch for it.
When a planet is approaching retrograde, it appears to slow down. It usually spends a few days in the degree that it's about to turn retrograde in. Once it reaches this degree, it's as good as retrograde, since it's not really moving ahead any more. Also, as the retrograde comes to an end, the planet slows down again; when it reaches the degree that it will turn in, it will again spend a few days there, and the planet is about as good as direct, since it no longer appears to be moving backwards. So when looking at these cycles, especially Mercury, which happens often, try to take advantage of the stations. As a matter of fact, since a planet that moves most slowly is far more powerful, when a planet like Mercury stations to go direct, it's at its most potent, even though (or more specifically because) it hasn't started to move forward yet.
See the following post for what to do when you're stuck with having to deal with daily life during one of these retrograde cycles.