Quick tips
Keep newly purchased plants moist and in the shade until planting. Preparing soil with organic matter is important, especially if the soil is heavy clay. Mulch with wood chips or other mulch after planting to reduce the need for frequent watering and protection of their shallow roots. Avoid using materials like re-cycled compost as it may have diseases not fully cooked out. It, like many other bark based materials will decompose to near nothing in a few years and generally farmers find better luck in planting orchards without soil amendments. With Maples, I think you should use a bark compound that won’t deteriorate like Fir Bark, Redwood etc. Avoid quick decomposing materials like Alder or Cottonwood chips even though they are cheaper.

Keep pruning of newly planted trees to a minimum.
Do not fertilize newly planted trees until the second growing season. Using organics or Time release fertilizer like Osmocote is fine as they will not release until the soil warms up in Spring. Use of hydropills is also advised. These will last for up to three years and are ideal for container planting.

Provide morning sun and afternoon shade and try to avoid windy or wind tunnel situations.

When to plant

Strangely enough the ideal planting time is in the Fall!  If you plant in the fall you take advantage of the dormant season root growth. Unlike the tops of the maple that go dormant and cease growth for the winter, roots of maples continue to grow throughout the fall and early winter months if temperatures are not below freezing. Fall planting also allows seems to be directed to root growth since there is little demand from the top. If you are planting in spring try to avoid disturbing any plant parts that recently has broken bud and is producing new, soft growth. Best of all Fall purchased plants are often discounted by the nursery.

Where to plant

Most maple species are naturally under story plants, but as gardeners we have forced them into the open landscape. There is a great degree of stress tolerance between the numerous cultivars Young trees will need to be protected from the elements until they have formed established root systems. Do consider the geographical source of your cultivar as Japan has many climate zones and not all Japanese Maples are equally cold tolerant. Korean and Manchurian Maples are much hardier.

The placement of your tree can mean the difference between an attractive lush growing maple and a straggly struggling one. With so many cultivars to choose from this should not be a problem as you should be able to match your landscape situation with the right cultivar. Try to match your maple cultivar to your planting location with regards to the amount sun, wind exposure and space availability the tree will receive. I would add that if you insist on planting Japanese Maples in S. Florida or the windy corridors of the Rocky Mt. states that you may have problems.. Japan has relatively mild winters and more rainfall in the summer than most regions of the U.S..

Morning sun and afternoon shade will suit most maples best. Wind and hot sun can wipe a small tree out in no time, regardless of the cultivar.   Leaves will show signs of stress with burning on the tips. So will over fertilizing. Sometimes in the nursery or at home the roots will become sun baked and the stress will show up in the leaves just like from too much sun or wind. Maples are thin-barked and can be sun scalded during the first year or two after transplanting. This injury can set the trees growth back considerably.  It is also a factor to be considered in climate zones that can swing from very warm to freezing at night. This can lead to the splitting of the bark and may well invite diseases.

 Soil Preparation and Planting in Clay or poor draining soils

Most maples do not thrive in clay, heavy or poorly drained soils. These types of soils can lead to root rot and bring about disease.   In addition plants breathe through their roots and these soil types are not suitable for growth because they are low in oxygen required for good root growth.
If your soil is heavy clay, make the planting hole 2 to 4 inches shallower than the root ball. In poorly drained or heavy clay soil, the plant is best placed higher than its original planting depth at about 4 to 6 inches higher than the surrounding. The addition of most soil amendments may be worthless after a few years as they decompose and start shrinking that height factor. In organics such as perlite as other amendments will fail less quickly.
In well-drained soil, the planting hole should never be dug any deeper than the height of the root ball, the planting hole should be at least twice and preferably even more times wider than the root ball. Roots will grow more quickly into loosened soil, thus speeding up the tree’s establishment time. Mulch should be placed over the surface. Young  trees should be staked with soft bindings and then released after a few years.
 
 Container Planting

 Planting in containers is a great way to start your maple tree. However, from years of growing maples in containers I have learned that Japanese maples prefer to be somewhat snug in a container. If too much soil is allowed to sit around the root ball there is a greater chance of the soil becoming too saturated with water which can become sour and lead to root rot. This seems to be particularly true for smaller maples in containers.
So it is best not to use a container that is too big for your tree. As a general rule use a container no larger than twice the diameter of the root ball and half again as deep.   Another way to look at this is not to go more than double the volume of the root ball.
As the plant becomes larger, planting in wine barrels or other large containers is a great way to use the maple as an accent on your patio, front porch or backyard. A general rule of thumb would be to de-pot the plant after three years, root prune and re-plant. The larger the container the more difficult this is to do. Another trick if doable is to tilt the container with a brick or too so the soil can drain better. Often done with Bonsai overwinter.
 
 Mulching

Mulch is a good friend of your maple. Mulch protects the roots from the heat in summer, the cold in winter and reduces the frequency of watering. Apply a loose mulch, such as wood chips or pine needles or straw over the planted area to a depth of 4 to 6 inches. Be sure to keep mulch several inches away from the trunk of the tree.   Be sure to mulch trees in containers. One negative being that a deep mulch under snow attracts voles and mice, so keep that in mind.  Putting down some mothballs might be a good idea.
 
Fertilizing

Everyone wants a bigger tree…now… but it is very easy to add too much fertilizer when trying to make your tree grow to fast and end up damaging your plant. In fact, most maples do not require any fertilizer for healthy growth. When trees are pushed with fertilizer it often invites disease and die back in the stems.
Always be careful with fertilizers!   The biggest mistake is to give the maple large amounts of nitrogen in the first and second years. A small amount of organic slow release fertilizer in the Spring would be much better for your plants. I have had real good success fertilizing in late April with  fertilizers such as bulb food. and alternate during the season with half strength Miracle Gro or like. If you are going to use inorganic fertilizers, it is best to fertilize lightly in half dosages rather than full strength..   Water soluble fertilizers such as Miracle Grow seem to work fine…but go lightly and use some organic liquid like fish fertilizer in the next fertilizing. Always at half-strength..

The timing of when to apply a fertilizer is also very important to keep in mind. Once transplanted it is best to wait and fertilize newly planted trees the second growing season after being planted. This gives the plant plenty of time to adapt to its new conditions.
Never put inorganic fertilizers such as dry pellets or fertilizer “spikes” containing nitrogen when planting a maple in the back-fill because root injury may result. Be careful with top dressed granular fertilizers which can sometimes release too much fertilizer at a time and thus cause damage to your tree. Homemade concoctions of organics such as bonemeal, cottonseed meal etc. may be made but can attract varmints.

Fall and winter is a common time to prune and shape deciduous trees and shrubs . Exceptions to this are maples which will bleed or ooze sap unless pruned when in leaf.  When maples are pruned in late winter or early spring the wounds flow with sap. If heavy sap flow occurs, pruning should be delayed until midsummer. This flow of sap can lead to disease invasion and weakening of the tree.   The preferred time to prune maples is between mid-July and August, a period when sap won’t run from cuts.   The one time when trees should not be pruned is during early spring when buds are breaking during leaf expansion.   Maples should be given a thorough pruning every three years and minor “touch up” pruning annually.   A thorough pruning involves removing dead limbs, crossing branches (or branches that will cross in the future).. This applies to Dogwoods and Magnolias as well

Give newly planted trees and shrubs only minimal pruning. Removing too much top affects the production of food energy (carbohydrates) and can result in poor root development. After planting, prune out broken branches and those with weak or narrow crotches. With young trees, leave some of the lower limbs and sprouts even though they will be removed later. These limbs provide the closest source of food energy for root development. I have also found that trees will form a stronger trunk if the lower branches are not trimmed for a few years. One strange tip being that you prune unwanted branches only above the first set of leaf buds. The plant still believes it has the phantom limb and will act accordingly. Over pruning may indeed encourage the plant to sprout upwards. Next year prune  these stubs down to the trunk. 

Hardiness of Japanese Maples, climate zones and diseases.

(C) Herb Senft