Here are a few of my favorite locations and some sample images from each.
Terry Hershey Park - Located near Wilcrest and Memorial. This is a great park for morning or evening sessions, it has a lot of open space, a path looking spot, trees and generally gets some good color later in the season.
Ray Miller Park - Located in West Houston, Eldridge near Briar Forest. This is a great place if you like the look of a bridge or something wooded. It works for both morning and evening, however evening is my favorite.
South Blvd - Located near Rice University. This is a great spot, morning or evening. It is very classic and provides the most BEAUTIFUL trees around. It is simple and timeless.