I've only recently started to sign my art again, i didn't for the longest time
i do a lot of commissions and i don't want anyone claiming the work as their own.. i sign my name and the date
K. Neuman March 15 2010
i'll write small and line it up with a part of the existing lineart
Example
i find it blends in okay this way
also when it's something i really like and i post it on DA i will add a watermark which is super easy since DA does it for you