Night shots on pier - need techinical advice bad!

[shesells]

Shot these last night. They are exactly the way the scene looked. All I did in PS is minor exposure correction in levels. A tiny S-curve, resize and usm in a small amount. I know there are problems with them that I could fix but I'm not interested in fixing them, or cropping them, what I want is to figure out how to take it right to begin with!

When shooting in the day, I instinctively know what to do by using the histogram and visually looking through the viewfinder. At night, basically I'm constantly guessing. I know it should be a somewhat long exposure, but how long? Then should I compensate with EV setting or ISO setting? What I did last night was start out in shutter Priority mode. Guessed at the time and took a few shots in different shutter speeds. Then I tried Aperture Priority mode, figuring I had to use a large aperture to let in more light. Well, I felt so uncontrolled that I ended up just using the Scene modes - twilight. I felt like that was cheating. Basically, In the past I've taken some great night shots but truthfully, they were all accidental! All I do is guess till I get it right. Next time out.. same thing.

So, if you looked at these scenes, as is, what would your photographic mind tell you when preparing to take the shots? I have read tons of stuff, but I feel that every situation is different. What I'm looking for is to hear others workflow when in the field. How do you judge the amount of timed exposure for instance? What do you actually think after the tripod is set up?

I don't want to resort to the automatic modes but it's bothersome to always be second guessing myself. Am I alone?
Thanks for listening and also for anwering.
Kit