RJI: I'm late contributing to this thread, but it's a very interesting question; thanks for posing it!
It seems like everyone agrees that the best way for a single person to find a partner is to put him- or herself out there a little more more. (I wish I had done this when I was young and single.) It improves the odds of success and provides practice in approaching others so that it hopefully begins to feel natural and comfortable rather than forced or awkward. What biglynch said about just having fun rather than going out with a specific goal in mind also seems like good advice to me; a connection with someone is probably more likely to happen organically when someone is relaxed and not stressing about the outcome.
I think both men and women tend to know right away in most instances whether they are attracted to someone or not; although personally there have been occasions when I was not attracted to someone at first glance, but when we got to know one another, he became extremely attractive to me.
Getting to know someone is never a waste of time.
I love this sentiment!
Also, perhaps I am hopelessly old-fashioned, but the idea of hooking up with someone whom one knows nothing about (even his or her name?!) sounds dangerous to me on a number of levels.
bigmac makes a good point about not investing emotional energy in wishing for a relationship to be something other than it is, but so does biglynch when he said that some women are more reserved than others and may be written off too quickly. Confidence is an attractive trait in both men and women, but I always assumed that men who were outgoing in general but aloof with me were just not interested. I'm not saying that a man should pursue a woman with an air of desperation or allow himself to be used as an emotional crutch, but I think that showing genuine interest in someone you're attracted to is a much better approach than trying to affect disinterest for strategic purposes.
And to answer the original question:
1) Bigger men often seem more approachable to me, as agouderia said. Perhaps because they are not perceived, physically speaking, by most people as God's gift to the world, they are sometimes less arrogant (at least in my experience); although everyone is different, and it's probably not wise to generalize too much.
2) A man's size, to some extent, suggests his willingness to indulge in sensual pleasures, which can definitely be a good thing.
3) Like many of the other women here, I find the tactile aspect of being with a bigger guy very appealing, although I probably wouldn't use the word "cuddly." Not because I can think of a better term; it just makes me think of Winnie the Pooh or Snuggles the fabric softener bear

, which is not really what I want to think about when I'm with an attractive man.
4) And, finally, as others have stated more eloquently, I'm not sure anyone can adequately explain why someone's looks are pleasing to him or her *shrug*; I just think a lot of bigger men are nice to look at.
