I always thought the only thing you ever really needed to activate a Sigil was blood or semen but other practitioners suggest meditating on the Sigil. Having feelings such as lust, anger or even sadness helps activating the Sigil.
When i first did it, i actually meditated for about a year and that was non stop. I had the sigil in my mind most of the time.
Just trying to figure how it all works and i thought it would be an interesting topic.