As i am reading into this whole "raising money" topic recently, this is what i came across in Venture Hacks.
My understanding is, shop around, but, don't say it as "shop around". Use other languages or excuses.
http://venturehacks.com/articles/shop-around
This is the summary:
Summary: A deal is only as good as its best alternative. Keep improving your alternatives until you have a signed term sheet. And keep developing your current offers or they will die. Finally, don’t say "shopping around", it puts investors off their stroke.
What are you supposed to say, "I have a very good feeling VC X might offer me 4, so you are going to have to offer 5." You can't haggle unless you have concrete alternatives to push the price up.