I would like to introduce you to the Rosh (Dean) of the Vaad Mishmereth STaM, Reb Dovid Leib Greenfield. He is a person that I have a lot of respect for. He has shown a tremendous depth of understanding of the seforim dealing with hilchos stam, from the gemara through the rishonim andto the poskim. He has also fought many battles on behalf of the mitzvos of tefillin and mezuzos. He is pictured below center examining an old sefer torah.
Rabbi Greenfield gave me a great deal of excellent safrus advice on a number of occasions. Two points stick out in my mind: He told me to purchase the sefer Mishnas HaSofer by Reb Yaakov Meir Shtern. Mishnas HaSofer is a commentery on the famous sefer Kesses HaSofer by Reb Shlomo Gansfried. This sefer, he explained to me would be as valuable as my sofer’s knife. I cannot emphesise enough how correct he was. Without this sefer, it would be almost impossible to have a truly solid grasp of the intricate halachos envolved. Just to give you an idea of how well used my Mishnas Hasofer is, I included a picture of it below the picture of Rabbi Greenfield.
The other point that he made was that just because someone has smicha from the Vaad Mishmeres Stam (or from somewhere else), it doesn’t mean the the Vaad becomes responsible for mistakes that that sofer makes! It seems obvious enough, but I have met both soferim and customers that don’t fully appreciate this point. The Vaad can certify that someone knows the halachos, and appears to be a trustworthy person, but they can’t certify that every set of tefillin that he wrote is kosher. How could they? They are not inside his head. They aren’t watching every move he makes while he is writting. The Vaad makes sure that the sofer is capable of writting kosher tefillin. The sofer himself must assure the customer that he actually did write kosher tefillin (or mezuzah or sefer torah etc.). 
