I know that I've mentioned searching in city directories before. You've probably searched and made notes so that you can enter the information into the software that you use for your tree. I don't know if you've done this, but it's worth mentioning: once you've located your family member in the city directory, enter his/her street address in quotation marks into the keyword field of the card catalog to bring up other residents of that address. Don't forget to add this information to your timeline if you're creating one to track your ancestor. This is especially useful in between census years.