So here are seven themes that you can apply to tricks to make them stronger and increase their impact. When possible, I've suggested an easy magic trick from here at Magic.About.com that the theme can be used with.
1. The Detective
With this theme, you don't claim any magical powers, but state that you have enhanced observation skills to read subtle changes in body language, facial expressions or voice, or rely on fingerprints, DNA or whatever suits your routine. Perhaps the best easy trick on the site that can be used with this theme is Dark Magic where you look at spectator's body language to determine the object that they secretly selected.
2. Looking Into the Future
Just as if you have a crystal ball or a special mental power, how about predicting what will happen in the future? I've got a lot of tricks that I can suggest for this theme, in fact, an entire collection of easy prediction effects.
3. Time Travel
The ability to travel through time offers lots of possibilities for magic tricks. You can start with a certain situation, mix it up, and then magically return to it at the end, just as if you've traveled back in time to the point where you started the trick. For example, this could apply time travel to a coin trick where you bring a coin from out of your pocket and place it under a handkerchief. The coin vanishes and returns to your pocket, back where it started.
Time travel can also be applied to tricks where you freeze time and cause something to happen. Again, this can include causing something to go from one place to another, changing colors, writing a prediction, providing something that you've written in the future and more.
What if you could really travel back and forth through time? You'll probably think of lots of possibilities with tricks that you already perform.
4. Breaking the Law of Physics
Many magic presentations talk about a new kind of technology, alien force or psychokinetic phenomena that causes strange things that break our world's physical laws. You can take a real science and exaggerate it with a new, experimental form. You can even make up your own technology. As an example, when presenting Daryl's Presto Printo, an effect where blank cards strangely pick up the images of other cards, I've been known to talk about a new kind of a high-tech printing process.
If you perform Magnetic Cards or Levitating Ring, you can talk about an alien force that is used to propel space ships that you have learned to harness (could be the result of that alien abduction that you underwent the other night?).
5. Reading Minds
What if you could see into the minds of others and identify what they're thinking? Or how about a Star Trek-style Vulcan mind meld or Star Wars-style Jedi mind trick? For this, there's the Killer Prediction and The Mind Reader.
There are lots of possibilities when you talk about harnessing the power of your mind, as with telekinesis, to move objects or make things happen that are beyond physical means. For this, I can think of several easy tricks that include: Banana Buster, you cause a banana to cut itself using the power of your mind; Cold as Ice, you cause water to turn into ice and Rising Ring, a ring somehow rises. And just as with reading minds, there's lots of possibilities for Jedi mind demonstrations (these are not the droids that you are looking for?).
Finally, if you want to get creepy, you can get into all that paranormal communicating with dead people and ghosts. Where and how far you take this will be up to you. And remember, you don't have to get morbid. You can "communicate" and "call-up" a friendly or playful ghost that causes something strange to happen.
I hope that I've helped get your creative juices flowing. Remember that by applying a premise to your tricks, you're not only enhancing the presentation and drawing spectators in, you're adding another thing for users to think about - it's basically mental misdirection. All it takes is a suggestion to take a simple magic trick and make it more convincing and entertaining.