How are you displaying the images on the TV, specifically?
What comes to my mind is to calibrate the display gamma on your computer, then use the TV's settings to bring the gamma into line on that device as well. There shouldn't be a need to prepare images specially for a TV.
Here's a neat little chart that when displayed at 100% original size on a computer monitor will help you get your gamma adjustment close to right. Try to make the big vertical bars look like single, smooth gray gradients. You should *just* be able to make out the boxes in the upper-right dark bar, but the lower-right bar should look pretty much black.
I want to display photos shot as JPG from a DSLR on a TV. When played on the TV they seem dark and lots of detail gets lost. Can anyone provide some general advice to make my images look good on a LCD TV? I am pretty new to Photoshop, would I just play with the Levels?
Like Noel said, you should be adjusting your monitor, not your images which are (presumably) already corrected. Most TVs are not well adjusted out of the box. As a first step, if your TV has picture mode controls on the remote, try a preset with a name like Cinema, because if your TV is set to a preset like Sports or Vivid the picture is probably too garish and unrealistic.
If that's still not good enough, you can go into the TV's picture adjustment controls and tune it further. You can play back an image like Noel's, or if you happen to have a Lucasfilm or Pixar movie, you might find a utility called THX Optimizer in the disc setup menu. This will guide you through some tests and adjustments for calibrating picture and sound (see link below).
If you like spending money, there are TV calibration discs that go into more detail, or hardware you can buy that will calibrate a TV very precisely.
Some of the newer flat screen tv's (maybe all of them by now, don't know) have a connector for connecting a computer to it, either a VGA, DVI or HDMI depending on your video card, heck maybe even a s-video connector may work.
Using a laptop connected to your tv you can place a puck on the TV screen and adjust the RGB controls and maybe white balance if the TV can do so. To calibrate the TV. Generally speaking it won't be as acurate a your default monitor, but it will get you in the ball park. The exception would be when you plan on playing video or photo's from the computer that connected to the TV, then you can use the full calibration process.
Most computer stores and Amazon carry monitor calibrator's for roughly under 100 and up. If your serious you should already have one anyway.