I'll post my IR workflow ... so just to warn you now... this post might be painfully long.
For IR shots I'd consider the "ideal" scene one with LOTS of sun but a few clouds in the scene, lots of foliage and preferably some still water.
To shoot IR I use a Hoya R72 filter (around 40 beans) with my kit 18 - 55 lens (might be the same kit lens with your D40) RAW format and a tripod. I put the cam on the tripod without the filter and set up the shot.
Stop the lens down to F8 - F11 or so because the IR light comes in differently and the camera has trouble focusing on it. So if you use a bigger DOF you don't have to be precisely focused on the subject.
Once the shot is lined up I switch the camera to manual focus and leave the lens on auto focus. This keeps the lens motor engaged and won't let the focus ring turn while you screw on the IR filter. It also doesn't let the camera attempt to refocus the shot once the filter is on. I know the D40 doesn't have a focusing motor so this step might be irrelevant.
With the shot composed and the filter on you can start shooting. I usually start with exposures around a 1/4 second and just watch the LCD for blown highlights. Adjust the SS as much as needed and once you think you have a good exposure bracket the bejesus out of it. I usually end up with 10 exposures.
Throw those exposures into a RAW conversion program (I use RawShooter Essentials 2006) and adjust the WB based upon any foliage. At this point is should start to resemble a typical IR shot but it will likely be flat. Convert that to Tiff or Jpeg and load it into Photoshop.
In Photoshop go to Image > Adjustments > Color Mixer. Grab Red from the pull down menu and make the blue adjustment 100% and the red 0%. Grab Blue from the pull down and make the red slider 100% and the blue 0%. Hit ok. Hit Auto Levels (or adjust them manually via a layer filter mask if you know how).
I usually create a Hue / Saturation Layer Mask and desaturate any color that might be hanging around on the foliage (usually it has a slight cyan tint) until the foliage is gleaming white. If you want to adjust any other colors go to Select > Color Range and grab the color you want to change. Once selected create a Hue / Saturation Layer Mask and by hitting Colorize in the menu you can adjust the colors.
That should be your final product though I find I can usually tweak the Levels / Curves / Colors a bit more after the automated processing is done and still get some more contrast.
Hope that helps. Good luck and if you're still confused shoot me a private message and I'll help you through the best I can.
*My disclaimer is that I'm at work and doing this off the top of my head so if some of the Photoshop menu names aren't exact... that's why.
Here's a link to some of my IR shots
http://www.wheresmymind.net/photopages/index.php?gallery=./Infrared Shots
They're definitely not the best shots in the world but should give you some idea as far what the final product could look like.