Traditionally tulpas aren't created by a singular person, nor consciously. However thought forms are like tulpas and are similar to servitors, but I agree that creating a sigil for this purpose would be appropriate for the suggestions Peyote mentioned as well as to keep "it" anchored to you. Also if it would help; you could try using the forum search feature and look for a post I wrote, on a previous account, on tulpa's. thought forms, and servitors. Just type in tulpa in the search bar, also I am sure there are many other posts on the topic that you may find helpful and useful.
