I have never had a sigil work for me. I must have done about 30 on topics such as business, love, lucid dreaming, astral projection and improved magic, and the only thing I have achieved is a single lucid dream that lasted about 10 seconds. I think that is more likely the result of my dream journal than the sigil.
I use the format "It is my will that… (statement in present tense)", eliminate any letters that have already occurred in the statement and simplify the sigil.
I have tried charging the sigil with meditation, pain, masturbation, physical exhaustion and chanting. I have tried staring at the sigil and visualizing it mentally. I have tried keeping the sigil, I have tried burning it.
Of course, early on I probably didn't let go. So I made a bunch of sigils and left them for two weeks, then did them as a shoal. I only had a vague idea of what one or two of them did.
Nothing works.
It is pretty frustrating, because if I can't make a sigil work, how can I expect to do stuff like evocation?
What can make a sigil fail? What am I doing wrong?