The informal upright bonsai style, or moyogi, is a variant of the formal upright style. As the name implies, it is less formal and is usually styled to be somewhat asymmetrically.
This style is one of the easiest of all the bonsai growing styles, and a good place to start if you are new to growing bonsai trees.

Form of the informal upright bonsai style
In the informal style, the trunk of the tree bends slightly to the left or the right, while the branches are trained in the same fashion as the formal upright bonsai style – regularly spaced getting closer together towards the tip of the tree.
Branches usually start approximately one third of the way up the trunk, as in the formal upright, but with the informal version of this style, it is not essential. Because of the curved trunk, informal upright bonsai can be better off having the branches start higher up, or lower down depending on the particular trunk shape.
The crown of the informal upright tree is usually allowed to develop dense twigs and branches, just like the formal upright bonsai. The crown is positioned above the base of the bonsai tree, to compensate for its curved trunk.
To achieve the slanting trunk of the informal style, the roots of the bonsai are trained to grow forward towards the front of the pot. The trunk and the roots of a tree usually grow in opposition to each other, and so when the roots are to one side, the trunk will slant in the opposing direction to compensate. This is alternated to produce a trunk that curves from side to side.
The trunk is also allowed to grow and thicken for a time, and is then cut back. This process is repeated, with the cut begin made higher up each time. This produces a good solid trunk that will form a strong base for growing dense branches.
Best trees for informal upright bonsai style
You can choose deciduous species for the informal upright because they look good during autumn and winter time, especially if your bonsai has abundant dense branches.
Some of the best species for the informal upright are Japanese maple, pomegranate, crab apple, beech and most conifers.