The two best strategies that I found working at a preschool daycare center was to format my reading sessions as theme days and to incorporate a blank poster (made out of butcher paper) that was a challenge to the kids to fill up with names of books that they read at home, at the center, or with me the idea being that reading wasn't just for once a week.
The themes had their pros and cons but overall I recommend them. Use themes based on the kid's preferences and try to stay away from broad themes that require more than the one or two hour sessions that you have with them. If you want to use a broad theme try to work it out with the teacher you work with so that s/he can have build-up activities all week. Another good idea with themes is to have the kids figure out what the relationship between the books are. Finally, try to have your last book tease the kids for next session's theme.
If you decide to use themes there are some great books that are indispensable that I have listed in the works cited. Books that list children's books in categories or even strategies for themed reading are great and your public library will have many from which to choose.
The biggest tip for reading to pre and early readers is to utilize your librarians! They are in touch with your population everyday and know about classics and new books that fit any category (and they probably know how successful the books are too).