That being the case, to start I feel it appropriate and pertinent to note that I do not follow a method akin to AO Spare's work - I do not use an Alphabet of Desire or such system save for when working with bindrunar, and even then, its a guideline rather than a set thing.
Generally speaking, I get the sigils directly from the spirit(s) I'm working with and/or interpret what I see, sense, smell, and so forth into a written form carrying the energy thereof. It's something done with one part instinct, one part intellect, one part inspiration, one part spiritual guidance, and one part art, really.
Rarely do I take inspiration from the work of others, as this is a stream of consciousness thing rather than an overly intellectual assessment of the essence of what I'm capturing.
When necessary, I intuit the intentions of the spirit into the sigil as well, sometimes tying it to specific a specific person or set of persons, allowing it to work for them and no one else, or other times its an open-ended ordeal.
With any luck, this will serve as inspiration for you folks to do something similar.