Arctostaphylos is in the Ericaceae ("heather" family). Another of my favorite plants is Arizona madrone (Arbutus arizonica) and is also in the Ericaceae. It has red papery bark like the Manzanitas, but much more elongated leaves and can form actual trees.
A. patula "Green-leaf manzanita" This is the species you don't need to worry about. You may see it in central and northern Arizona. It is a low thicket former in coniferous forest at higher elevations (7500 to 8000 feet). It is reported to have leaves that are distinctly more bright green than the other species.
A. pungens "Point-leaf manzanita" Ignore the "point leaf" business. What distinguishes this plant from A. pringlei is that it has glossy leaves rather than hairy leaves.
A. pringlei "Pringles manzanita" This has sticky hairs, especially on younger growth. The leaves are more grey and hairy than P. pungens, and the plants tend to be bigger and softer looking" Arizona Flora calls this "glandular pilose". If you have a hand lens, take a look at the hairs with tiny clear balls at the ends!!
Once you spend some time in the field (I studied these plants up in the Santa Catalina Mountains north of Tucson) you can recognize these plants at a distance. They are often intermixed, and I have yet to find elevation ranges any kind of clue. If you grab some young branches on A. pringlei they will stay stuck together -- and they feel somewhat sticky.
Both can get quite tall (up to 8 or 9 feet) and form extensive thickets at elevations from 5000 to 7000 feet elevation, especially on south facing ridges and slopes such as near Windy Point.
Tom's Plant pages / tom@mmto.org