When you are playing Roller Coaster Kingdom, you will have things called ride lines - pretty obvious here that they are what your customers stand in to get on your rides! The first thing we would want to do is make the lines as long as possible in order to lock customers in to riding it. Unfortunately that isn't a good strategy in this game, because customers will get disgruntled and leave the line.
How do I make my lines better?
This is very similar to how things would work in real life - if you are sick of standing in a line to get on a ride, you will probably just leave the line and look for something that is quicker to get on. Make sure that as you are building rides, lines, etc. that you think about how long the ride takes to complete because this will affect how long your customers will be standing in line. For faster rides, you can get away with making longer lines because your customers will move through them quicker. Slower rides should have shorter lines for the same reason.
Make sure the white arrow is there!
If your lines don't have the white arrow pointing to the ride, your customers won't be able to find the ride. This means that people will just walk right by it and not even try to get on because they don't know where the line starts.