Before starting this article, I recommend you view this article:
http://www.create-games.com/article.asp?id=1988

Several techniques I use are included in that article, and would cause this article to make more sense.

First, start off by making whatever background you want to use
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It doesn't matter what your background looks like, or if you have a particularly differnt style than mine, this technique should be quite universal, barring a few exceptions.

Now we're going to create our lightsource. Rather than draw it up, I'm a pain in the butt so I select the area I'm going to draw over with the marquee tool.
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Then, I just up and delete the area.
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Then I fill it in with the color of the fixture, deselect the portion that is the fixture and work my way up until ive colored in all the areas with the desired colors. Since my background is a brown, I selected an extremely light version of brown, which comes out to beige. For lightbulbs and other transparant objects that you are drawing that aren't over a transparant field, use the color of the background behind it, make it more pale and possibly with a bit of a yellowish tint if you can.
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Go ahead and shade in the fixture, so it looks nice and neat (my mouse is extremly messed up, it has a problem with the left click, it only clicks sometimes, so bear with me, its shaded.)
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Now, using the technique in the last article, select your brush, turn down the opacity and flow, and instead of using a black or white, set the color of the brush to the exact color of the background behind it and start clicking away at the middle. (quick note, the opacity and flow settings are totally up to you. I use alot of quick and short strokes, so I set it low to cater towards the massive ammount of clicks I make, which is problably why my mouse is going "let me rest damn it". if you dont use as many clicks, turn the opacity and flow up to match your style)
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As you can see, it starts to make the bulb look more transparant, so continue shading in your bulb.
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In my background, there is a dip in the wood represented by the darker line, if you select that color of brown, start painting that on your bulb following the line.
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You can also select white as your color and add kind of a light shine effect at the top part of the bulb, granted this is not a great example drawn here, but mess around with it yourself to get an idea of how you want it to look.
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Now that we have our unrealistic looking lamp with no shade or anything, were just going to turn out the lights. Start a new layer and fill it completely with black.
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Now, you're problably thinking, "Why Chloe, why don't we just set the opacity of the layer down and be done with it?" Well, you could do that, but we're going to take this a step further. Select your eraser tool, and set the style to brush.
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Make sure you have the opacity and flow set all the way to 100% Set eraser cursor to one with a large size that is very soft (they are the ones in the brush menu that aren't completely solid and have a kind of glow around them) Then float your mouse over the lightbulb (if you don't have x-ray vision like me, feel free to set the opacity of the layer down so that you can see through it)
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You should see something similar to this image here.
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We're not done yet. Start a new layer and go back to your brush. Set your brush opacity and flow all the way to 100% and select a pale yellow color. Click once over your lightbulb and viola!
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That's all there is too it, as far as photoshop is concerned. To use these in MMF, simply import both the black layer and light layer (either separate or together based on your need for them in game), and chance the opacity in MMF to suit your needs. You could set the opacity in Photoshop and import it there, but that's more for those who have a static lightsource with no need for time changes, or a on, off switch.

Hope this gave some people some insight into lighting, go crazy with it, and have fun!