The key to long exposures
I enjoy shooting long exposures. The longer the better, unless that is you're stood on a very noisy motorway bridge in a very cold wind.
I've posted on shooting long exposures several times over the years (for example "Silky Water Shots" and "Breathtaking examples of long exposure photography") but as it's something I really enjoy doing, I thought I'd write another slightly more up to date one.
There are 3 key elements to a long exposure photograph; a steady camera, some way of triggering the shutter without touching the camera and a camera with the functionality to shoot 30 second + exposures.
To keep the camera steady you need either a tripod (unless I'm shooting people I'm on a tripod 95% of the time anyway), something like a gorillapod or at a push even a bean bag on a wall will suffice. If you trigger the shutter with your finger, you will incur some camera shake. It's inevitable. There's no way round it. If you are shooting a portrait in a studio with lights and all, then you'll never notice, but if you are making a 15 second exposure you will blur the image by pressing the shutter. Even if you use the daintiest of fairy type touches.
The only way to get round this is by either using the self-timer or my preferred method of using a cable release and mirror lock-up. 
The cable release is essentially a shutter button on a cable which avoids you having to touch the camera. I also go the extra step of using mirror lock-up too, which removes one more item that could cause a little vibration and thus blur the image.
Finally, a camera that has the ability to shoot long exposures. Some point and shoots just won't let you do it. But ideally you want a camera that will let you make exposures that are as long as you like - this is called Bulb mode. Why it's called Bulb mode I have no idea. For example, my Nikons will go as slow as 30 seconds and then the next step is bulb. This is where you absolutely have to have a cable release - you can't keep your finger on the shutter button for 60 seconds and not expect a blurred image, unless maybe you are well practiced at impersonating a corpse.
Cable releases go for anything from a few pounds up to several hundred. I think from memory Nikon's version of the cheapo that I use is around £250. I balked at that figure somewhat and I have to say that (fingers crossed, touch wood) the £30 imitation I got from eBay a couple of years ago hasn't failed me once - though it's definitely seen better days and I think it's probably nearing the end of it's effective days...
Anyway, the image at the top was taken yesterday evening from a footbridge overlooking the M6 at Shevington near Wigan looking South. Unfortunately I got held up getting there and missed the actual setting of the sun, but arrived shortly after. I opted for a little neutral density by way of my Singh Ray Vari ND in order to darken the scene even further and give me the endless trails of car lights I was looking for. A pretty sky would have made this image much better, but that's what happens when men decide to start digging up huge trunks of the highway completely out of the blue.....