One of the most rewarding ways to paint I have encountered in watercolor painting is painting my vacation pictures. This had become one of my ongoing projects for years. Most of them were done from photographs but a few were done on location. Creating paintings from photographs is so much more convenient and easier than location as it saves so much time and makes the process less rushed.
You should begin each piece of artwork by studying the photograph and determining what are the important points that you want to accentuate. Write down your thoughts or ideas about the photo, so you can reference them while you paint. Playing background music is a huge help when you're creating and can help make a mood for your creation while helping you paint better. You will get lost in the mood of the music.
When choosing photographs, it is necessary to eliminate some things from the photo and choose only the things that make the painting come alive. To begin this process, just draw in pencil, lightly, on the paper the scene that you would like to keep.
Once you have the scene in pencil, begin painting in the background. In watercolor, you should paint from background to foreground, letting each stage of your painting dry before you begin painting another.
When painting from photographs, it's not necessary to make the painting look exactly like the photo. It is your idea or creation of the photo, so you as the artist should paint it as you see it, not as others see it. This is the freedom of being an artist, whether you are an amateur or a professional.
When you're blending your color for these types of photos, you should completely use your imagination. Colors and shading can be used in completely different ways. If you are going to do the snow, you could do shadows of the trees in a lavender color or even blue colors. They really look awesome this way in watercolor.
Feel free to blend colors that will express how you see the photo which will bring life to your work.
Creating paintings from photographs takes time and practice. It is something that you work at and grow into. Your artwork may or may not come alive for you right away but if you continue to open your mind and your soul to the paint and brush, you will be rewarded.