Hi Believer,
First of all, i'm no expert on J.maples but i've grown some nice ones on my property. If it's still in a nursery container, get it in the ground. If your soil is heavy, dig in some sand and peat to loosen it up. Pick a spot where it's not in sun all day. A spot that gets afternoon shade.
Plant the root ball a bit higher as opposed to too deep and put about 2in. of mulch over the planting area. As to watering, you'll have to be the judge. They like a moist but well drained soil. When it starts to look better,hit it some acid fertilizer, like Miracid at half the recommend dose. Hope i was some help to you. I live in Mich. My soil is very sandy and has been amended with top-soil and shreded oak leaves. I'd attach a pic of my 15ft.'Blood Good' beauty in the front of my house but haven't learned how to attach a pic with a message yet. Good Luck

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Japanese Maple in search box.