I have started collecting scarves just in the last nine months or so, so I am a relative newbie, but here is how I've gone about it (this is long, but it helps me out, too, to put it in writing, so I hope you don't mind)...
Regarding eBay: I have been pleased with a lot of my ebay purchases. I try to buy them systematically--I have a wishlist that I don't always stick to, but I am always familiar with designs/colorways I purchase and have been thinking about them a while. I've had great experiences with sellers recommended on tPF and have dealt with other good sellers too--usually collectors who may only sell scarves occasionally and take the time to post detailed pictures and descriptions of condition. I'm often tempted by low prices, but I try not to buy anything I don't want enough to pay near retail for, even if I don't actually end up paying that much.
As for choosing scarves: I have to like both the design and the colorway, although often one will grab me more than the other. There are designs I really like that I just can't find in suitable colorways or don't look right on me, so I haven't bought them. I generally gravitate toward intricate designs, usually more whimsical than literal in their depictions of animals (I think most of my scarves have animals on them) in bright, saturated colors; I like designs that relate to things I've long been interested in (places/cultures/etc.), although I don't limit myself to those. They should also tie well; if there's not much going on in the corners of the design it probably won't be that interesting when it's worn.
Inevitably there is some trial and error, but I've had a pretty good success rate buying scarves I love.
And I have to say, there's nothing like a brand-new scarf from the store crisply folded in its orange box. I have my grails, but I really love the scarves I've bought in the store, so maybe if you're not just feeling your ebay scarves you should stick to the boutiques. And in the boutique, as
elle tee said, you can try on a lot of scarves and get a sense of what works on you. Oh, and to echo another thing she said--I just washed a couple of my scarves for the first time (there are several good threads about washing scarves) and they're very clean and touchable, so if I did happen to receive a scarf that needed a good washing I would have the nerve to do it now.
I hope that helps!
