ABOUT:
どう and いかが mean "how" or "in what way" or "how about …" いかが is more polite, but they are interchangeable otherwise.
Examples:
気分は、どうですか?
How are you feeling?
すしは、いかがですか?
How is the sushi?
お飲み物は、いかがですか?
Would you like something to drink?
最近、仕事はどうですか?
How is work recently?