In each horoscope, there are benefic lords, malefic lords and neutral lords.This is based on the house they rule and is not related to the natural classification of planets as benefics and malefics:
The Benefics or benefic lords are:
First house lord, other than Moon,the 5th and the 9th lords,lords of the 4th, 7th, and 10th when they do not happen to be natural benefics.
The Malefics or malefic lords are:
Lords of the 3rd, 6th and 11th houses,lord of the 4th,7th and 10th if they happen to be natural benefics.
The neutrals or neutral lords are:
The Moon when he is lord of lagna, the Sun or the Moon as the 8th lord, the Sun or Moon as the lord of 2nd or 12th house.
Yogakarakas are the planets that confer fame, honour,financial prosperity etc.Any planet can become a yogakaraka when he is common lord of certain houses.
A planet owning both a Kendra(quadrant) and a Trikona(trine) becomes a Yogakaraka.
Mars, Saturn and Venus can only become the Yogakarakas based on their lordships for some ascendants.
Cancer and Leo Ascendants: Mars becomes the yogakaraka.
Libra and Taurus Ascendants: Saturn becomes the yogakaraka.
Capricorn and Aquarius: Venus becomes the yogakaraka.