One scene, two different moods:Example A:
Midnight approaches and tattered clouds speed past the waning moon. Naked trees claw at the sky with skeletal fingers. The wind attacks you with its icy bite before hurrying onward to rattle the frozen weeds, and kick up swirls of snow. Wincing at the stab of the cold air, you clutch your cloak closer about you and slog on toward the lurking keep.Example B:
The sunglow fades and a few fragile wisps of cloud float past a pristine moon. Slender branches, silvered by moonlight, sway to the song of the winter wind, and swirling puffs of snow dance among the white-clad wildflowers. Snuggled safe in an enveloping cloak, you drift down the path towards the castle.
Many descriptions depend on adjectives, but adjectives are like icing: Too much makes some people feel quite ill. Try to adapt your adjective usage to the style of your piece, but even in the most florid style have pity on people's mental digestion and try use adjectives only as a flavoring, and not as the meat of a passage.
The strongest, most dynamic words in English are the verbs. Careful use of verbs creates instant atmosphere. Compare the verbs used in the first example: speed, claw, attacks, hurrying, rattle, kick, clutch, wincing, slog; with the verbs of the second example: float, silvered, sway, dance, snuggled, drift.
Here are the above passages with no adjectives. Notice how a mood can be carried by the verbs alone.
Midnight approaches and clouds speed past the moon. Trees claw at the sky. The wind attacks you before hurrying onward to rattle the weeds and kick up swirls of snow. Wincing at the stab of the air, you clutch your cloak around you and slog on towards the keep.
The sunglow fades and clouds float past the moon. Branches, silvered by moonlight, sway to the song of the wind, and puffs of snow dance among the wildflowers. Snuggled in a cloak, you drift down the path towards the castle.
Another tool that can be overlooked in pursuit of yet another descriptive adjective, is the use of nouns. In English there are frequently many different words for the same thing, each with a different emotional quality or feel. Did you notice how in our examples the weeds became wild-flowers and the keep a castle? Also note that we established the time once using the foreboding 'midnight' and the other time with the much friendlier 'sunglow'.
A careful choice of descriptive metaphors is another good way to alter nouns and influence the mood. To create a tense uncertain atmosphere in the first passage I compared the tree branches to a skeleton, and personified the wind as if it was an attacking beast. In the second passage I described the sound of the wind as a song, implying harmoniousness.
Another thing to keep in mind is that English can be very grammatically flexible, and it is frequently possible to turn nouns and verbs into adjectives and adverbs. The 'swirls of snow' in my first example became 'swirling puffs of snow', in the second because I wanted to create the same mental image, but with a connotation of fluffy harmlessness.
One last thought: Try not to lump your descriptive words together. Although for my examples I used paragraphs that were almost entirely descriptive, in an actual story it is very rare for me to expend more than a single sentence on description alone. I write stories, after all, and stories have forward momentum. Feel free to scatter your description throughout the main action. Far from lessening it's impact, the way the description and the action interact tends to heighten the effect.
As midnight approaches, you feel the urgency of your search increase. How long can Landi survive back there if you do not find help soon? High above, tattered clouds speed past the waning moon, and their racing shadows make it harder to find the path beneath the snow. The indentation that you hope marks the way turns left, winding it's way toward a stand of naked trees that claw at the sky with skeletal fingers. You eye them dubiously, hoping they will provide a little shelter. As if sensing your treacherous thoughts, the wind attacks you with its frozen bite before hurrying onward to rattle the frozen weeds, and kick up swirls of snow. As you turn toward the trees your steps start dragging. It seems like you have been traveling through this waste forever, but where there is a road there must be people. Peering ahead into the darkness you think you see a blocky shadow materialize from the darkness, far too regular for a hill. Could it be that you have reached the end of the road at last? Is this the fortress of Northgate? But if it is, why is it so dark? Where are the welcoming fires and bright torches that you have been hoping for? Wincing at the stab of the cold air, you clutch your cloak closer about you and slog on toward the lurking keep.