Repot your topiary as soon as possible. Most of the pots in which they are sold are too small to maintain good root growth, which your topiary plant will need to sustain good health and support its shape.
Feed your plant, especially if it is growing in a pot. Remember, potted plants don’t have the freedom to search for added nutrients outside their original growing area. Foliar or slow release plant foods work well.
Water often, even if the plant is outdoors and has the benefit of rain. Topiary shapes can change the way water is absorbed, especially if the plant is in a pot.
Trim in early to mid-summer when the plant has the best chance to recover from pruning. Most will only require pruning once or twice a season.