The basics you need to know to paint landscapes well.

In landscape painting, we need to understand the dominance of value, temperature, and intensity. We also need to be clear on our design, the focal point and especially why we want to paint the idea. Additionally, using techniques that provide depth and perspective are key to the success of our landscape painting.
Landscape Painting Basic # 1: The Big WHY.
We need to begin with the idea or theme. Basically this means asking Why am I painting or drawing this idea? or What is inspiring to me about this image? Perhaps it the way the light hits the masses, or the type of light (hard, soft, ethereal). Is it the interlocking shapes; the mood or the way the river meanders through the space? Be clear about the theme before beginning. This way all the elements can be used to support the big why.
# 2. The Format
Choose the best size and format for your idea before diving in. For example, is it square, portrait, landscape view, long and narrow, small or big?
#3. The Design

The design is your blueprint. You need one before you begin painting. At the most basic level, decide if your image is about the foreground, mid-ground or background and make one of these use a majority of the space. Big sky, small earth type of thing. Secondly, have a primary focal point. Keep your focal point away from centre, unless you have a tonal value plan to make it work. A common device is to put the focal point near the crossing of third lines or golden mean intersections (a ratio of 1.618).

Following is a list of design ideas:
S-Curve or Z, curvilinear, arabesque, cruciform, mass or cluster, pattern, linear or strata, alphabet letter such as the capital letter L, H or A, frame-within-a-frame, perspective. Repeating shapes and use of reflections create harmony. Following is a list of Edgar Payne‘s composition ideas form the book Composition of Outdoor Painting, an oldy but a goody:

#4 The Viewpoint
Always be aware of the placement of the horizon line. Are you level with the horizon line, above it or below it? This basically is knowing if you are looking up, down or straight at a view. For example, you can be on the same level as the trees, looking up at the trees, or looking down at the trees. Unexpected viewpoints can make for interesting designs.
As an aside, I read about a psychological study where 200 people were asked to draw a tea cup on a saucer. All 200 drew a side view. No one drew an aerial or a low view. Interesting. Andrew Loomis’ book, Creative Illustration, does a good job on showing the viewpoint idea.
#5 Perspective and Depth

As in architectural drawings, landscape elements have perspective rules as well. For instance, cumulous clouds close to us will be deeper than those in the distance. The clouds in the distance flatten out considerably, as will mounds of earth, waves, grasses, rocks and so on.
Perspective can be a way to create depth in paintings. A winding road or river disappearing into the distance, or a fence line, are great perspective devices. Also, overlapping shapes, done correctly, add a sense of depth into your painting.
Another way to create depth is use of brush strokes. For example, use bigger strokes in the foreground and smaller, flatter strokes in the background. More texture in the foreground than the background is another option. Texture in drawing can be accomplished with various types of broken marks, or continuous tone for less detail. The movement of your marks, whether in drawing or painting, can explain shape and depth to the viewer.
Aerial perspective is another concept to be aware of in landscape illustration. Objects further away, such as mountains, will look cooler, duller and less detailed. There are exceptions to this, such as in some areas where the air is so clear that distant objects are also very clear.
And Landscape Painting Basic #6: The Value Plan, Temperature and Saturation
Create a tonal value plan, including whether your painting is dominantly low, mid or high key. Always (always!) know your light source. Also consider how to implement lost and found edges during your tonal planning. Click here for Mastering Composition Using Three-Shade Studies.
Here are blocks of greys showing four tonal plans:
Tonal Values of Landscapes
Below is a general idea of how values are in landscape painting. The exceptions would be a bright light on snow or sand, which can make the ground lighter than the sky.
Temperature and Saturation
Also, as with any type of painting, decide if your painting is overall cool or warm. Decide too if it will be overall bright or neutral.
Feel free to check out my favourite art books for more ideas and inspiration. The more you learn about landscape painting basics you need to know, the better your paintings will become.
Better methods – better paintings!