Saraswati Yoga

To understand Saraswati Yoga, we have to re-look at the basic nature of all the planets. 

Benefic - Jupiter, Venus and Waxing Moon. 
Malefic - Rahu, Ketu, Saturn, Mars and Waning Moon. 
Mild-Malefic - Sun. 
Neutral - Mercury. As Mercury is neutral planet, it takes the nature of the planet it is sitting with. So, if it is with Jupiter, it becomes a Benefic Planet and if it is with Saturn or Rahu, it becomes a Malefic Planet. 

So, Saraswati Yoga occurs when Jupiter, Venus and Mercury, all the benefic planets, either sit together in one house in Kendra/Trikona (i.e house # 1, 4, 5, 7, 9, 10) or if they are sitting separately, they should be in Kendra Houses only (i.e. Houses # 1, 4, 7, 10). 

Impact of this yoga is that as all these planets are benefic in nature, so their benefic impact on individual increases manifold. Especially, if any of the 3 planets is exalted then it is surely blessings from the heavens. Its more profound impact will be seen in Kendra or Trikona Houses. In other houses, it will lose its strength a bit. 

Real impact will be that this person will be highly learned, wise, of pleasant personality and intellectual. As all three qualities are coming together (Jupiter-Wisdom, Venus-Beauty, Mercury-Intellect), this is one of the rarest of rare good yogas. This person will be well read. He will acquire knowledge from any available source. House/Sign in which this yoga is occurring will decide the subject of knowledge acquired. Similarly, They will be one of the best orators of their time, as Mercury (communication skills) is getting support of Jupiter (Knowledge & Wisdom) and Venus (Beauty). Overall, the prime objective of this person will be to attain knowledge through any source. House and Sign in which this is occurring also play an important role. In other houses, the yoga is not that strong but in Mahadasha and Antardashas, it will throw its impact on individual and create circumstances in which he will be tempted to attain knowledge and wisdom. And as it gives loads and tonnes of knowledge and wisdom, this is known as Saraswati Yoga, as Goddess Saraswati is the Goddess of Knowledge, Education and Wisdom. 

This is very basic description of this yoga, Further research is surely needed. 

Swami Premanand Bharti