If you have the 2E product
Warriors & Priests of the Realms, there is a not-so-evil specialty priest of Shar described therein known as a Darkcloak.
Here are some quotes:
Overview
Despite Shar'’s evil alignment and her being the goddess of night, darkness, and loss, there is another side to the goddess, a side that is actually beneficial.
The Darkcloaks are members of Shar’'s clergy that function as oracles and care-givers to the emotionally damaged. The Darkcloaks bring the bliss of forgetfulness to such troubled souls. The Darkcloaks have actually made some progress in seeing Shar'’s faith become a socially acceptable one.
Role-Playing
Darkcloaks believe that life is full of pain, and only the emotional oblivion of Shar makes it tolerable. Unlike their nightbringer brethren, the darkcloaks actually have compassion towards the sufferers of mental anguish. Preferring to cultivate a reputation as mysterious folk, the darkcloaks frame their oracular proclamations in obscure riddles and mysterious symbols.
Ultimately, though, Shar is about nihilism. Hers is not the destruction of the Abyss or the Elemental Chaos but the end of all things to bring things back to the ultimate emptiness of the beginning.
IMC, Shar is interested, inter alia, in releasing the elder evil, Pandorym, so that the deities of the Realms are destroyed. If that happens there would be nothing holding back the primordials and they could return Toril to its original unmade state. (If you accept that line of thinking then Shar would also be the one behind the FR equivalent of Greyhawk's/PoL-land's cults of elemental evil.)
Also, as Shar is ultimately about nihilism I can imagine various factions within the Shadovar who are none too pleased that the deity that they are supposed to venerate only wants the end to everything when they would personally prefer conquest or empire building. IMC, Bane as the deity of tyranny and Graz'zt as his demonic counterpart both have strong followings amongst the Shadovar, although this is considered heretical. (And Graz'zt might have a particular attraction to the krinth, who are the shadar-kai descendants of shadow demons.)
Anyway, the opportunity to include representatives of cults of elemental evil, Bane and Graz'zt amongst your encounters does provide you with a bit more variety. (And if you do use the Graz'zt idea, please make sure you include at least one skulk with the spectral assassin template and then post here about how that turned out [please].)
As for being in Shar's favour, anything that strikes against hope, particularly on a large scale, is likely to attract her favour. Similarly, anything that strikes against Selune pleases her.
