What settings should I start with for low light? 35mm f1.8 prime.

[Fedaykin]

If the D40 has TTL (or is it i-TTL) metering and a built in flash, use the flash. If you have to calculate the settings, it does become a little more difficult but with TTL it's fully automatic. Having a fast lens is good and setting a higher ISO will hopefully get you to the correct shutter speed but unless you really can't use a flash - use it. You are limiting yourself to "an aperture setting" and/or "a ISO setting" and it will affect your photos. It is amazing how much light the camera's flash will produce assuming you're not trying to get a far subject. Having a shallow depth of field won't work in certain situations.

Low light is difficult to work in and there may be times where using a flash is not practical. I myself have bought a new camera with the intention of using a high ISO when need be but plan of using the built in flash whenever possible. I expect that the high ISO photos to be somewhat noisy but figure that's better than no photo at all.

Can you explain why you suggested he use the built in flash with a prime lens. I got my 35mm so I wouldn't have to use flash and then got an SB-600 just to enhance my pics a bit with bounce. Just seems like weird and confusing advice.

You get a SLR to take better photos and to have more flexibility not to not use flash. Even with a f 1.4 lens you are going into higher ISO in low light situations. You are limiting your DOF as well as limiting shutter speeds. Try taking a group shot with 3 or 4 levels deep of people set at f1.4 - you'll have a lot of unfocused people. Use a flash, set a mid f stop (f8) and get them all focused and in the picture. I can't speak of post processing a photo as I don't spend a lot of time playing around with my photos yet. The built in flash is better than nothing to not limit yourself. Now you have a bounce flash - you need to learn to use that if you haven't already. The bounce is a great thing - no harsh lighting and it takes some of the shadows away but it does have limitations as well. A direct fired flash has more range than a bounce and if you ever try to bounce off a 20 foot ceiling - it isn't going to be much light.

To Gaerek: Here's something to consider - not everybody has money to spend on all the photography equipment they want - some people need to work within their means! Using the camera's flash will do just that, it is your opinion that they are worthless - they do what they are intended to do - put light where it is needed.

Here is a photo using the camera's flash without knowing how to really use my new camera ... personally I don't think it did such a bad job. Would a bounce flash or a more elaborate setup do a nicer job probably.

And this is why we say pop-up flashes suck. Look how unappealing it makes the subject look. As Gaerek said you'll get better results by using higher ISO and shutter speed, etc. He WOULD be working within his means.