Filling out printed forms (e.g., checks) independently is currently impossible for blind people, since they cannot pinpoint the locations of the form fields, and quite often, they cannot even figure out what fields (e.g., name) are present in the form. Hence, they always depend on sighted people to write on their behalf, and help them affix their signatures. Extant assistive technologies have exclusively focused on reading, with no support for writing. In this paper, we introduce WiYG, a Write-it-Yourself guide that directs a blind user to the different form fields, so that she can independently fill out these fields without seeking assistance from a sighted person. Specifically, WiYG uses a pocket-sized custom 3D printed smartphone attachment, and well-established computer vision algorithms to dynamically generate audio instructions that guide the user to the different form fields. A user study with 13 blind participants showed that with WiYG, users could correctly fill out the form fields at the right locations with an accuracy as high as 89.5%.