Here are some really good thoughts on the topic of propagating plants from cuttings and similar methods.

from Wendy

The easiest types of plants to grow from cuttings are those which show little nubs of growth tissue next to the joints in the stems. These will almost immediately root, if you bury the nubs. Plants include pothos, christmas cactus, euonomus, and creeping cotoneaster.

The next easiest type is softwood cuttings of shrubs with flexible branches, such as forsythia. Personally, I prefer to layer, rather than starting cuttings. Layering is bending down a shoot of the plant, and burying the joint while still connected to the mother plant. This keeps the shoot alive while rooting, and is much, much easier than cuttings. I am currently layering a five-leaf aralia. It takes months to get good roots... you can see that a cutting could easily dry up in this time.

The hardest plants for cuttings are woody plants. Azaleas and rhododendrons are difficult to propagate by cuttings. (more on these -- click here)

from Un-named contributor

I've always had good luck with just about any cuttings but I always use root tone powder. Then treat them like babies until they are standing on their own. Gotta keep an eye on those "kiddies", & don't expose them to harsh elements (wind, heavy rain, drought, etc.) until they are strong enough to handle it. Use a good potting soil with compost and water them regularly (don't over water). To produce roots they must be kept moist while young.  Some flowering plants like impatients, begonia, etc. I just put in a cup of water (change often to keep clean/use rain water or distilled if you have treated tap water) 'til I start seeing roots then plant.
 

Rhododendron and Azaleas
from Steve Henning in Reading, PA   USA

Most evergreen rhododendron and azaleas may be propagated from stem cuttings. Cuttings are usually taken in the early fall from new growth that is just hardening off. Cuttings are taken in the morning when full of moisture. The cuttings are usually terminal cuttings with one whirl of leaves with the leaves cut in half (to reduce the leaf area) and any flower buds removed. The cutting has the end cut off just before placing in hormone powder (containing a fungicide).

Then the cuttings are placed in a flat of sterile media containing a mix of 50% peat moss, and 50% horticultural perlite or vermiculite. The flat is placed in a polyethylene bag with struts to keep bag away from the foliage and placed in a light area with no direct sunlight. The flat is rotated once or twice a week to compensate variations in light and temperature. Usually bottom warmth of 75°F is used to encourage root growth.

Rooting usually takes about 6 weeks for evergreen azaleas and 3 to 4 months for large-leaf rhododendron. Once the cuttings have rooted, pot or transplant them to flats containing a sterile mix of 60% peat moss and 40% perlite. Fertilize once a month with an acid-based azalea plant food like Peters. Removing terminal buds promotes sturdy well branched plants.
 

Visit my Rhododendron and Azalea web pages at:
http://www.users.fast.net/~shenning/rhody.html

Also visit the Rhododendron and Azalea Bookstore at:
http://users.aol.com/rhodyman/rhodybooks.html
 

by Ann, Gardening in Zone 6a, Just south of Boston, MA

Although Azaleas and rhododendrons are difficult to propagate by cuttings, some of them do respond well to layering, as you mentioned.  This is much easier than propagating by cuttings.

Just find a suitable branch that will reach the ground about six to ten inches from the tip.  Slice a little notch diagonally into the stem.  Bury that slice in the ground and put a rock on top.  Leave it alone over the winter, at least.  In the spring, check for roots.  If they are there, I'd still leave it alone until the following fall, even.  Then cut it loose and transplant it to where you want it.

Yew
from Un-named contributor

Over the last three years I have tried to turn an unruly fencerow (100 yds of poison ivy and wild grapes)into a thick yew hedge. Every late summer I collect yew twigs and root them. Here is what works:

• Take twigs that have old (brown) wood. Green wood tends to fail.  Late summer when the energy content is maximum.
• Not too big, or they will have trouble developing adequate roots. Not too small, or they will be covered by dead leaves and die. 8-10 inches is about right.
• Slant the cut so as to maximize the open wood. Dip into rootone.
• Plant in 4X4X4 plastic pot with potting mix (actually I use half milk cartons, holes poked in the bottom). Soak in water and keep soaking wet until ready to plant.
• Keep indoors through the winter. Plant in april after one week in sheltered place outside. When planting, allow pot to dry by stopping watering 20 days before. This will facilitate removing the whole block of potting mix. plant twig and bloc of mix, soak.
• Keep away from direct sun (just a few dead branches over it for partial shade) and water occasionally the first year.