This subject is a perfect way to practice watercolour techniques.
Wet on Wet – A peach is a way to practice this technique. Have a palette prepared of a lemon yellow, an orange, a red and a crimson. These should be made up in separate washes. Wet the area of the fruit with an appropriate sized brush. Paint on the yellow and let that soak into the paper. Take a clean brush and apply some of the orange wash to the top of the fruit but tilt your board as you work to move it down the middle of the fruit. Use the end of a brush, or an old spent biro, to impress in the line that is evident from the centre down to the bottom of the fruit. Take a stipple brush and add stipple of red, let that soak in and then stipple on the crimson.
Glazing – A leaf is a way to practice this technique. Underpaint the leaves with a lemon yellow, a yellow ochre and a medium yellow on separate leaves. This is to give variation to your green colours. Mix up a variety of greens, form a lemon green to a dark green. You can add any colour in your palette to adjust a green. Add a green colour to a leaf and then impress draw the veins on the leaf, so the yellow colour shows through.
Wet on Wet and glazing together – a tree trunk is a good way to practice these techniques together. Have a dark brown and a light brown ready your palette. Underpaint the tree branch and trunk with a yellow. Whilst still wet, add in a line of your dark brown and with a light brush stroke drag that across the shape of the trunk. Near the edge of the other side of the trunk paint in some of the light brown.