I'm not a a professional photographer but here's my way of taking night shots.
Yes, you do need a tripod to take good pictures at night.. (learned it the hard way) but if you came across a good scene to take the photo and have no tripod, you can try finding a good spot where you can stabilize your camera. Find anything like railing, a wall, just almost anything that could help.
For example:
In this picture, i didnt use a tripod but instead, i hold my camera while my elbows rested on the bridge's railing.
hope this helps