Now right off the bat you need to know that not all women love to shop in the same way. They don't even all like the same kind of dress shops. Your gal may love high end stuff from Nordstroms while your best buddy's gal may adore hole in the wall boutiques. So don't assume they will be buddies and go shopping so you and your friends can hang at the pub. Ask first, okay?
Don't wait until she asks you if you see something different about her. If she spent three hours deciding on which way to color her hair, don't you dare not see that it is dark brown instead of soft brown. The best bet is to take pictures often and compare. When in doubt say, you look great babe, new hairstyle? Just don't ask her if she has gained weight, ever.
Many men just don't understand that springing an early morning fishing trip on her is not the kind of surprise she will be excited about (unless she really does like fishing). But springing a planned trip through autumn leaves in New England, she will understand that. If the surprise has a hot tub and romantic fireplace at the end, you get brownie points.