Straggly plants are unsightly but can be encouraged to bush out by pruning back some of the top growth. If you look at a long shoot, you'll see that there are small buds at the base of each leaf. The bud at the tip of the shoot is dominant and will continue to grow. If that is removed, however, the side buds, the ones at the leaf bases, will sprout. So instead of one long shoot you have many shorter ones. Whenever possible, cut the longest shoots at a point below some lower branches that will hide the bare stems.
Take the longest shoot of your plant and, using sharp pruning shears, cut it back about 1/4 inch above a leaf node, the place where the leaf attaches to the shoot. Choose a node that is slightly below the tips of shoots or branches around it. Make the cut at slight angle to the stem rather than directly across it. This helps moisture to flow away from the cut.
Take your next longest shoot and, again, cut it back above a leaf node that is hidden by the surrounding growth. If your flower or plant has no shorter stems, don't worry. Cut back the longer ones about half way. The new growth this forces out will soon hide the cuts.
Continue removing a third to a half of each shoot that seems especially long and leggy.
Take each shorter branch and remove the tip, the dominant bud. This will promote bushy growth on these branches and prevent them from lengthening.