Various usages of どう

どう carries the meaning of 'how', and it can be used in various ways. Examine the following:

• "how" (asking manner of an action): どう読みますか。/どう書きますか。

• "what": どう思いますか。(What do you think?)
  (Note: Don't say, 何、思いますか。to mean 'what do you think?')

• "what": 休みは、どうしますか。(what are you going to do during the vacation?)
  You can say, "休みは、何をしますか。" here. The difference between
  「休みは、どうしますか」 and 「休みは、何をしますか」 is that the
  former asks "how you arrange/deal with/handle the vacation" whereas
  the latter asks concretely "what kinds of things you do during the
  vacation.

• asking for advice: お金がない時は、どうすればいいでしょうか。

• "how about?" (suggestions): このケーキ、どうですか。