What species did you get?
I deflasked some phalaenopsis hybrids for the first time in July. They are still alive and growing. I keep them in the humidity tray, water by misting the moss with very weak solution of balanced fert 20-20-20.
Here they are just after deflasking:
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You got some good advice above. One thing to find out from the vendor is how long they have been out of flask. If they literally were just deflasked, I'd really try and keep the humidity up like Orchideya has suggested. If they've been deflasked a bit longer (>1 month or so), you can start to lower the humidity slowly, but should still try and keep it up a bit.
Most seedlings dont like wild temp changes, so be as diligent as possible to keep them at a stable(ish) temp. Other than that, a lot will depend on your cross/type for more info, so lets have it!