In Vedic Astrology, there is a specific principle of the planetary aspects. Firstly, here the planetary aspects are considered and not the aspects of the concerned houses.

Secondly, these planetary aspects have to be complete in form and not in an incomplete form. Thirdly, the positive or negative effects of the natural bodies are permanent and not temporary. Besides,  the basis the planetary aspects is also natural.

But Lal kitab has a different principle
(1) Here, the aspects of the houses are taken into consideration. If a planet is in a particular house, then the aspect of that house has an impact on the planet. For example, the first house has a complete aspect on the seventh house. So, if some planet is in an ascendant, that planet will also have a complete aspect on the seventh house. But if that planet is in another house, then that planet  will no more remain under the impact of the first house.
(2) According to Lal Kitab, the aspect of a house can be complete(100%) or half complete(50%), and even one-fourth i.e 25%.
(3) Unlike Vedic Astrology, according to Lal-Kitab, the favorable or unfavorable impact of  the celestial bodies is also temporary. For example, if there is some natural enmity between Saturn and Sun and Sun is in the first house while Saturn in the ninth house. Then Saturn  which is in the ninth house is the base of Sun which is in the first house. Hence, here, Saturn will support Sun.
It means, according to Lal-Kitab, the natural friendly or unfavorable relationship of planets is less important. Since the mutual relationship of planetary aspects or the relationship of different houses will alter the mutual relationship of the planets.

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One more difference between Vedic Astrology and Lal Kitab.
According to another principle of Vedic Astrology, an aspect of every planet is seventh. For example, if Sun is in the third house,and is looking at Moon which is in the ninth house, then the Moon of the ninth house will also look at Sun in the third house .In other words, there well be a mutual relationship in the aspects of Sun and Moon.

In Lal Kitab, on the other hand, though Sun of the third house will look at Moon which is in the ninth house, the latter will not look at Sun which is in the third house. In this way, according to Lal-Kitab, there is no mutual relationship between planets nor is there any negative aspect of the houses. Hence a person can easily understand Lal Kitab.