The letter is drawn by starting with the horizontal "roof", drawing from left to right, and then drawing the vertical line from top to bottom. It is important to ensure the horizontal line extends slightly further on the right, so as to distinguish it from the letter Resh.
Just as Gimel is the charitable letter, Daleth is the poor letter which receives Gimel's charity. This aspect comes from the shape of the letter, which, because it is "bent over", resembles a beggar looking for charity. It is also because of the root word for this letter, which is dalah, to impoverish , which, in turn, gives rise to daluth, meaning poverty.
Daleth is related to Chesed via the number four, and its relationship can be seen through the aspect of poverty, for Chesed is the first Sephirah outside the Supernal triangle, and thus is "impoverished" in comparison to them. There is also a relationship between the just and merciful aspect of Chesed, as the residence of the Chasidim and Jupiter, the just and righteous god, and the notion of poverty, both in the vow of poverty taking by many righteous people, and the act of Gimel, of giving aid to those who are impoverished. Thus, these two letters create a symbiotic process, for the poor need the rich and the rich need the poor.
The number four, being the number of Daleth, is particularly evocative, for there are many mysteries to this number, not least of all the Tetragrammaton. Because Chesed is the first Sephirah outside the Supernal realm, it can be seen as the first proper expression of the elements, and this occurs through the number four, and the Tetragrammaton. It is often said that Da'ath cannot be crossed while in the physical body, and thus Chesed is the last "physical" Sephirah, as it were, although it is very far from the physicality of Malkuth, where the elements find their fullest expression. Daleth is the doorway through which the Light of the Supernals reach the other Sephiroth, and also the passage through which the ascent back to these Supernals is accomplished.
Daleth is also the doorway to Scripture, for there are four levels of understanding such, and they are terms Pardes (PRDS), the orchard, which is a notariqon of Pesheth, the literal understanding, Remeze, the allegorical understanding, Derash, the exegetical or interpretative understanding, and Sod, the mystical or "secret" understanding.
But this is not the only doorway that Daleth hints at, for this is a deep mystery in adding the letter Daleth to the Tetragrammaton. If we add this letter between the last two letters of YHVH, we get YHVDH, which is Yehudah, or Judah, the Jew. Thus it is said that the Jew is the doorway to God, and while this may seem overly in favour of Judaism, it could be argued by Christians that this hints at Christ, who was a Jew, and is the doorway to God. This is also shown in the assignment of Christ to Tiphareth, which must be passed through before union with God in Kether ("No one comes to the Father except through me").
Daleth is a Double Letter, meaning it originally had two pronunciations ("d" and "th"/"dh"). It is also, as a Double Letter, given a planetary assignment of the Sun in the Kaplan GRA translation, as well as Westcott's translation. In the Short, Long, and Saadia versions the planet is Mars, possibly because of its relation to Tuesday in the GRA version, but the other three opt for Monday instead. Its dual nature also relates to "seed" and "desolation".
"He made the letter Dalet king over Seed
And He bound a crown to it
And He combined one with another
And with them He formed
The Sun in the Universe
Tuesday in the Year
The right nostril in the Soul,
male and female."
Sepher Yetzirah (GRA version), 4:10
The path attributed to Daleth is called the "Illuminating Intelligence" in the 32 Paths of Wisdom (Westcott translation), while in Kaplan's translation we have the following:
"Illuminating Consciousness. It is called this because it is the essence of the Speaking Silence. It gives instruction regarding the mysteries of the holy secrets and their structure."