How to get my Nikon DSLR to focus in low-light settings?

So, I can NEVER take pictures when it comes to restaurants, bars, outside carnivals, etc.

Tomorrow I have a lunch thing and we wanted some good pictures and I really want my camera to focus. Currently it will just produce blurred pictures in low-light settings.

I'm in manual mode, have set my ISO to 1600, set it to white balance and shutter speed to 1/2 a second. The pictures come out bright in the low-light setting I made for myself but still won't focus on the object.

Any tips?

You've just identified the problem. Handheld photos taken at 1/2 second will be blurred unless done by extremely experienced photographers with supersteady hands.

Why in the heck are you shooting in manual? The designers and engineers of your quality Nikon DSLR have spend a lifetime to develop various modes that will allow all photographers to captures images in a wide variety of challenging situations.

The fact that you are shooting handheld at such a low shutterspeed tells me that you need either a faster lens, or need to use a flash.

Your problem is not focus, it's motion blur.

I'm not surprised they're blurred with a half second shutter speed!

That's way too slow!

There isn't enough light for the correct exposure at a decent shutter speed to hand hold (not to mention that your subjects are likely moving too).

You have upped the ISO but you still need more light. You either need a faster lens (f1.8 or 1.4) - but that will give you a shallow depth of field wide open) and/or you need to add light (use a flash).

The on board flash is not the best option but it'll do in a pinch. Ideally you want an external speedlight with a bounce/tilt head. That way you can get some 'depth' to your pictures.

If you are at a lunch and people are moving about and the lighting is low you need a flash to keep your shutter speed fast enough to freeze the movement. Even if you use a tripod to keep the camera steady the people are moving and will blur at slow shutter speeds.

The problem is not that your camera won't focus. Blurr is being caused by camera or subject moving during exposure. At 1/2 second you have no chance of holding the camera still.

Set your camera to aperture priority
Open the lens as wide as it will go
ISO1600
Set exposure correction to underexpose by 1 or even 2 stops - it's dark in there but your camera light meter will try to make it bright daylight. Shoot RAW so you can boost brightness levels a little if necessary in post process.
You should just about get away with exposure of 1/8th second (assuming you have steady hands, have image stabilisation, you hold the camera properly and your subject is rock still)
If exposure will be any longer than 1/8th then use a tripod, use flash or increase the lighting. If you can't do any of those then it is blurred images or nothing!

Final advice - Don't wave the camera around at arms' length using live view. Use the optical viewfinder, left hand cradling the lens, right hand firmly on the grip, elbows tucked into your ribs.

Put your camera on full AUTO!

Because at the moment you don't have the skill to use manual mode.

Next, open your user manual, and read it. Pay particular attention to the part about metering. You need to know about that if you are going to shoot in manual mode.

Next learn about the exposure triangle, how to meter your shots, and what shutter speed is for. Tutorials here for photography: http://www.cambridgeincolour.com/...colour.com

Okay, I'll just do a little list for you because it's easier. I'll just write out simply what it all is to help you understand where you're going wrong:
1. The ISO is the camera's sensitivity to light - the higher it is, the more it will pick up (but beware the higher ISO, the more 'light noise' - the bobbly, dotty effect on the image- the camera will pick up depending on the model of camera of course)
2. The aperture setting - they are the 'f stops' the lower the f stop number eg 1.8, then the larger the larger the aperture will be - the more it'll be open, letting in more light. The higher the number, the smaller it'll be letting in less light.
3. The shutter speed control how much light is let in too - faster speed, less light - slower = more. But it also captures motion faster speed freezes motion, slower speed will cause blurring.
All of these need balancing & you need to plan what effect you want to achieve as the end result.