To ensure your hair is healthy for sleekness, be sure not to over- or under-wash. Washing too much say once or twice a day, can strip your hair of natural oils that keep it looking smooth and shiny. Washing often, like once a week, may leave your hair dull and lifeless.
The next step is preventing as much damage as possible. Of course, some damage is inevitable if you color-treat and heat-style your hair, but protecting your strands with heat protection by using a protectant spray and finishing your look off with a smoothing treatment oil will help with frizz reduce flyaways and help you create a sleeker finish.