The first step in painting reflections is to first look at reflections. This is true with most anything you want to paint, first go look and study the real thing. Next time you are walking down the street and it is wet, look ahead and see what the sidewalk looks like. Check out how the sidewalk looks when someone is in front of you walking.
Then with your cell phone or camera, take a picture of the reflections. Don't worry about getting a well-composed photo to do a painting from, get it for studying how a reflection looks like on the sidewalk. If you have time do fast sketches on the spot, this will help you in memorizing what reflections look like.
Most important when painting a wet street is to first do it wet-into-wet, giving you the soft edges. Reflect the objects that are on the sidewalk or street
with a soft edge reflection, use the same color of the street but darken it to the value of the object. Then while it is still wet put a little color in the dark reflection that represents the color of the object, just a little of that color. To many students only put the color of the object in the reflection when they should be putting a darker color of the sidewalk first. This same principle holds true when painting reflections on water, like a lake. You can also do hard edge reflections but
make sure your values are not real dark, make the values close to what the street or sidewalk are.
Here I will repeat myself..... the best way to learn about painting anything new is to study it first hand, on the spot, look and see it and then memorize what you saw. Then another thing that will help is look how other artist's interpret the look of wet streets.