The keys to any good logo is the ability to quickly convey as much information (that's positive) about you as possible in as little visual real estate as possible, while still being easy and quick to read.
Some of that has nothing to do with the logo, but has more to do with your website. If your website name is tevotakesawesomephotossoyoushouldhirehim.blogspot.com, then your logo is destined to fail no matter how good it is, because it would be nearly impossible to cleanly guide people to you from that. Your logo, business card, watermark and website address all need to sync up. Even if you don't yet have a website, sometimes its good to go ahead and reserve the simple, easy to remember name before you put your logo out there.
Make your logo clean. Make it so that it's easy to understand quickly and easily identifiable. You want a logo that can be glanced at and understood within seconds. That's a near universal. Then, as far as the particulars go, that depends on your field. If you're doing wedding photography, you want to it to be simple, yet elegant. If you're doing architectural, you want strong and clean, etc. If you're doing general purpose for a lot of different clients, then something nice and simple and clean should work. But most of all, they should be able to glance at it, and within a second have a pretty good idea of what your website address is. Like if it boldly says "TEVO PHOTO" if it is at all possible, have your website be TEVOPHOTO.com. For a watermark, you can even add in a very small '.com' underneath your logo. Sure it makes it look a little less visually appealing, but it's more than paid off in communicating "hey, I have a website, and here it is, visit it." And that's the real point of a watermark, to get people to your website. Otherwise it's just vanity or naivety.