A movable Raashi aspects all fixed Raashi except the one adjacent to it.
A fixed Raashi aspects all movable Raashi except the one adjacent to it.
A dual Raashi aspects all other dual Raashi.

For example,
--Aries is a movable sign. It aspects all the fixed signs except the one adjacent to it, i.e. Taurus. So Aries aspects Leo, Scorpion and Aquarius.
--Taurus is a fixed sign. It aspects all the movable signs except the one adjacent to it, i.e. Aries. So Taurus aspects Cancer, Libra and Capricorn.
--Gemini is a dual sign. It aspects all other dual signs. So Gemini aspects Virgo, Sagittarius and Pisces.

Graha Drishti vs Raashi Drishti
A simple analogy will make things clearer. Look at planets as people. Let us take a priest as an example. Will he have some influence on his neighbors? Probably. Because he lives there, gets up early in the morning and recites Mantra, it may influence his neighbors also. Because of the houses they live in, his neighbors come under his influence. How pious and god-fearing his influence makes his neighbors depends on other factors. If one of the neighbors is a dreaded criminal, he is not going to be influenced.

Let us take a dreaded criminal as another example. He may also have an influence on his neighbors. Youngsters living in the neighboring houses may enter the criminal world because of him. Ladies in the neighboring houses may stay inside their houses at night and not come out after certain time.

Thus we are influenced by people in neighboring houses. Influence exerted by planets by Raashi Drishti is similar to this influence.

Compared to this limited influence on the neighbors, a priest may have greater influence in the matters of the nearby temple where he works. He may have a lot of influence on devotees who come to visit the temple and who approach him for performing Poojaas, Homs etc. Influence exerted by Graha Drishti is similar to this influence.

Influence exerted by Raashi Drishti is due to the sign a planet is in and this influence is due to the inherent nature of a planet. This is analogous to the influence people exert on their neighbors. All planets in a sign will have Raashi Drishti on the same signs, just as people living in the same house see the same neighbors everyday and exert some influence over the same neighbors. But the influence they exert may differ. A priest may tell his neighbors to pray to God. His movie-loving brother living in the same house may talk the same neighbors into watching all the movies of a particular actress. Similarly, planets in the same sign may influence planets in different houses. Thus, planets in the same sign exert influence on the same houses and planets through Raashi Drishti, but the nature of the influence varies from planet to planet.
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All 7th house aspects (oppositions) are full aspects.
75% aspects are those to the 4th and 8th Raashi counted from a Graha, except for Mars for which these are full aspects.
50% aspects are those to the 5th and 9th Raashi (Trikon) counted from a Graha, except for Jupiter for which these are full aspects.
25% aspects are those to the 3rd and 10th Raashi counted from a Graha, except for Saturn for which these are full aspects.

Never heard of 75%, 50% or 25% Raashi Drishti? They are not mentioned in most important classics, therefore we can take all Raashi Drishti as full aspects.

BPHS and others do not define special Graha Drishti for Raahu and Ketu, therefore the general rules apply for them - or they do not throw any aspect due to their shadowy nature. I do not work with Raahu/Ketu aspects - but of course with the aspects of the Raashi where they are placed in. Raashi Drishti are always valid, for Upagraha as well.