Dark Photography School

After the tripod and camera itself, the next most important piece of gear to own is a remote shutter release. This is a hand held controller either attached by cable or by infrared that can remotely open the shutter. Most models allow you to press once to take a picture normally, as well as press and lock which will hold the shutter open indefinitely when in bulb mode.

This is my off-brand remote, obtained at a local camera shop for around $15. The one made by your camera manufacturer is probably more than $100.

A remote shutter release is essential for many reasons:
The first - it greatly reduces camera shake. Even though your camera is on a tripod, the vibration caused by your finger pressing the button can produce blur on short to medium exposure times–especially at longer focal lengths (telephoto).
The second - it allows you to get candid photos much more easily. The advantage of a candid photo is that you will capture people in the way they are in real life. Simply frame the image, and then look in another direction. Wait a few seconds, and snap it.
The third - the ability to use your camera’s bulb mode. To utilize bulb mode, switch to manual, and move the exposure time past 30 seconds (on a Canon system).
I almost always have my remote plugged in to the camera while out and about, and I recommend the same to you. If you keep it in your pocket or camera bag, you are less likely to use it. At less than $20 (for the off-brand model), there is no reason not to own one.