You can do a half hour, flat, easy walk on the Pipe Track, the crazily popular, one and a half hour steep hike up Platteklip, the more adventurous routes up via India Venster or Kasteelpoort, or if you are really not into any effort at all, zoom up with the cable car and mill about on the large flat Table top. There are dozens or routes, of all kinds of duration, desolation, views and difficulty. Whichever one you choose, you won't regret it. I have hiked Table Mountain dozens and dozens of times (I live here), and each hike is equally memorable. Whether you want to spend the day on the mountain, or just do a quick-up-and-with-the-cable-car-down-after-work, Table Mountain has something for you. Don't miss out, you'll regret it when you post your Cape Town visit on FB and people comment with things like 'I hope you hiked up Platteklip' and add a selfie with unparallelled background views.
Two words of warning: be prepared. Whatever the weather, take some warm clothing, a snack and drinking water. A wear proper shoes.