It costs. I would throw about $100 a month at it and set my rate to like $1.70 per click. Couldn't afford it and there were no real benefits so I changed my rate to like $.20 per click. Every so often I get a hit.
Of course my website isn't designed or at all intended to attract wedding business so you may have better luck. But it just helps your chances of someone seeing your website. The higher you set your rate per click, the more often google will show your ad increasing the likelihood of generating traffic.
You have to be real clever with the words you choose as well. Entering "Wedding Photographer" won't do you much good, but a phrase like "Milky Way County Wedding Photography" or "Gothic Style Weddings" will increase your chances of being seen if someone searches for something like that. You have to really think of things you want to associate yourself with so that when people search, your name comes up. Like you're really into Jesus so if one of your adwords/phrases is "religious marriage ceremony" then it's likely google will place your ad on the sidebar of their search and if they see "faith based wedding photography" well that may be relevant to them and they'd click' and that click will cost you whatever your rate is.
Google has a great write up on the whole thing. And they even offer a spreadsheet to let you know which of your keywords are generating the most placement of your ad and the most clicks.
