I speak a lot at conferences and I got in the habit to categorize conferences into three types, which might help you deciding what kind of conference you want to go to.
The Big Commercial Ones: The big conferences are the ones well known in the industry. They typically have more than 1000 visitors. At such a conference you typically can expect some big names doing the key notes and lots of well known people doing many talks. Therefore lots of the talks have very high quality. Although the fee for attending is pretty high the organizers still need more money, which they get from an exhibition area where companies present themselves. Some of the key notes are sold to sponsors. Unfortunately these key notes tend to be really bad. I don't really understand why, because one would think if you spend a couple grand from your marketing money for a speaking slot you'd send the best speaker you have. Well companies like Oracle, SAP and IBM tend to send some marketing guy with screenshots. So when you at one of these big conferences and a key note comes up, check out the speaker and the company he works for. If the company is big and among the sponsors of the conference and you can't find anything interesting when you google for the speaker, it is likely you can skip the key note. Of course you can always go to learn from a bad example. If you have enough money, these conferences are an awesome place to learn, you'll find stuff for every knowledge level, except maybe at expert level. Not because the speakers aren't able to do that, many sure do, but the whole conference is aimed at a broad audience. If you want extract expert level information from a speaker you have to hunt her down, which might become difficult with such large audiences.
The Small Local Ones: These are conferences organized by mid sized companies. They are smaller, about few hundred attendees. There won't be many of the big names on the speakers list, maybe one for a key note and one or two additional talks. But lets be honest, most of the time we don't need "The world expert for X" to learn something about X. And there are a lot of things that are great about the smaller local conferences: There are many of them, so there might be one in the city you live in or the next bigger city. They are a lot less expensive, often offering discounts for students. Everything is smaller, slower more relaxed. Since there are less people, you will be able recognize them at breakfast, during talks and at lunch making it much easier to start conversations including conversations with the speakers. Often you can learn much more from chatting with a motivated developer from another company than from listening to talks from book authors for 2hours. These conferences are also much more open to new speakers.
The (Small) Community Events: These events are organized by the community, i.e. by user groups, software craftmanship groups and the like. They come in various sizes from SoCraTes with less then 100 attendees to pretty huge events like Devoxx with thousands of attendes, although most of the time they are on the smaller side. If you are a completely new to the industry it might be difficult to find the right content at these conferences, but if you have a little experience these are awesome places to be. Even at the small events you'll find highly motivated local experts, eager to discuss their latest ideas with anybody willing to listen. The 'talks' have more often an interactive approach. So if you just want to be fed information and links, these events are not for you. But if you really want to learn, get into contact with the community or want feedback on your own ideas, these are the places to be. Be prepared to stay up late and discuss until the early morning.