My night shots are troubleWhat camera features are most important for taking night photos?

how can i get a manual for this camera

First: Turn up the ISO to at least 800, if not 1600, this will depend somewhat on the light level you have to work with.

Second: Turn on "long exposure noise reduction" that's somewhere in the camera settings menu. With LENR on taking photos will become a timely process. The noise reduction function takes roughly as long as the exposure, so a 30 second exposure will take another 30 seconds to process but it is well worth the wait.

Third: Use a tripod, I can't stress enough how important a tripod is!

Fourth: Use a tripod! (Yes it is crucial for a quality low-light photo) If you don't have a tripod, or you've left it at home, try to find a stable spot e.g. fence post, table, chair, etc, where you can rest the camera while it's exposing.

Fifth: Use a shutter cable or remote control. This is not as important but can be very useful, especially if you not using a tripod.

Sixth: Turn on "Auto Focus Assist", also in the camera setup menu. As you may know the D70, when set to automatic focus, will not take a picture until it's found a focus subject.

Hope that helps.

Night photography can be tricky. Generally, you have to allow for long exposures, which can result in "noisy" (or grainy) photos. If you are interested in night photography, here are a few features to keep in mind:
High ISO numbers. Cameras with higher ISO numbers require less light for exposures. This means, you can take your night photo with a faster shutter speed and still get the same result (taking night photos with high ISO can result in noise, which impacts the overall image quality).
An allowance for long exposures. Long exposures allow the shutter to be open longer to absorb the available light.
Image stabilization features. This prevents movement during long exposures. Night scene mode, if it is available. This setting automatically provides low-light settings and doesn?t require you to manually modify the settings. This option is good for beginners who are still learning about the different available exposure options.
Noise reduction mode. Long exposures often allow noise ? or grain ? into your photo. Rather than use photo manipulation software to remove the noise, this setting automatically removes it for you.

Is there a way with PowerShot SD630 Digital ELPH to alter the shutter speed for good night portraits? Or am I limited to the presets?

A high ISO isn't all you should look for. Some cameras have 1600+ ISOs but the results are unusable due to noise. Read reviews to see how the camera performs at high ISO. The Dynax / Maxxum 5D is one of the best at high ISO with even ISO 3200 pictures coming out usable.

What about the best and most obvious soution, keep low ISO levels and USE A TRIPOD. Bracketting at a large differential will also pbably help.