Cotoneasters can be broad-leaf evergreens or can be deciduous depending on your zone and species. Cotoneasters naturally form to the cascade, semi-cascade, informal upright, root-over-rock, and raft styles wonderfully. They form fantastic mame and shohin sized bonsai. Be careful not to let too many shoots develop at one point as reverse taper can happen quickly if left unchecked.
Cotoneasters can handle heavy pruning and will back bud on old wood. Pruning is great on Cotoneaster because we can predict the direction of growth due to the alternating pattern of the leaves. Due to this you can easily style these trees through the clip'n'grow method.
Cotoneasters thrive in full sun with protection from afternoon sun in the High Desert. Allowing 6+ hours of sun would be best.
Wiring should be done in Spring. Since Cotoneasters are vigorous growers you should be careful about the wire cutting into the branch or trunk. Be careful not to pinch leaves under the wire.
Don't fully bare root your Cotoneaster.
Taking softwood cutting in early Summer is the best way to propagate Cotoneaster. They are notorious for being easy to propagate. I just did a softwood cutting in later Fall and stuck it in some potting soil and compost and it leafed out in Spring (USDA Zone 8/9). Really hard to mess up propagation on these guys.
I personally recommend these for beginners due to their durability. They don't have too many nuances to pick up on to be able to successfully grow and train them.
For a great example of a Cotoneaster progressing through it's Bonsai life refer to this Flicker gallery by Jerry Norbury: Cotoneaster Progression
For care guides on other species head to my Bonsai Information page.
To learn about specific species and their care head to my Bonsai Information page