For those wondering about hair accessories, I bought this a few months ago and really like it:http://www.drugstore.com/goody-comfort-flex-updo-barrette/qxp299224?catid=183396
I found mine at Target, but I've also seen it at my local grocery store. I think it also comes in a smaller size. The one I linked to is large enough to fit around all of my hair, even when it's doubled up on itself. I have not found many barrettes that are large enough to fit around all of my hair even in just a low ponytail, so that's a major plus.
I have shoulder-length curly hair right now, although it's still a little slippery and kind of unruly. When I use the barrette above, I gather my hair into a low ponytail, then twist it up (like I'm going for a french twist). I secure it by sticking the bar of the barrette underneath the twist (catching some of the hair right up against my scalp), and then securing it around the whole thing. Since my hair is short and curly, I just leave the ends sticking straight up, and they sort of curl around the rest of my hairstyle so it doesn't look like that's what I'm doing.
If my hair were longer, I'd probably try to find a way to tuck the ends under somehow.
The nicest things about this barrette are that it holds my hair securely without being too snug or hurting my head, it doesn't snag my hair when I put it in or take it out, and it looks classy. I've gotten several compliments on my hair when I've used it during work hours. When I've checked out the result in a mirror at home, it really just ends up looking like I created a totally awesome french twist and then stuck a decoration on it for show. Nothing holds my hair so securely that I can leave it alone for 8 hours at a time (unless there's a lot of hairspray involved), but this does well enough that I usually only have to re-do the style once during my average work day.
Another thing I've learned with regard to hair involves my bangs. I had longish side-swept bangs cut in several years ago, but I'm kind of lazy about keeping them trimmed. They are often long enough to get in my face and be annoying, so I often pin them back with bobby pins. One thing I realized is that the look where you pull your bangs straight up, smooth them out a bit, and then pin them straight back on your head (leaving a bit of volume at your hairline) can actually be a flattering look under the right circumstances. It works for me when I can get the right chunk of hair and smooth them out enough that there aren't lumps. Too wide or too narrow a section of hair looks somewhat odd, but it works if I use one that occupies about the middle third of my forehead.
Also, if you are going to pin bangs (or similar) back with bobby pins, use two. Crossing one over another so they form an X works well, but I've also found that just putting two in parallel to each other (but close together) can be a secure hold, too. Particularly when I'm just pinning my bangs back on the side of my face, two parallel bobby pins looks a little nicer to me than crossing them.