Just some quick tips for night shots...
1. Take them RAW everytime.
2. Err on the side of overexposed on capture, back exposure down on processing (these are overexposed as a final product)
3. Fix your color balance to correct for the various colors you'll see- you need to strike a happy medium, but these are overall very yellow.
4. EDIT: I knew I was forgetting something- always do manual focus on night shots, and if the subject is far off manually focus to inifinity. (be sure to know where infinity REALLY is on your lens before you go for the shot, it isn't always marked correctly or at all)
Some general tips...
1. Straighten those horizons (most of these appear slightly tilted)
2. Correct for barrel distortion in your lens (you can see it in some of these)
Very good start, though! Keep at it!