There are several things I would recommend doing to help you keep your park clean. I’m thinking you already do some of these, but I thought it might help to share anyway.

If you want to clean up your park, you need to use Handymen. They can be hard to control sometimes. Here are some tips to help you manage them.

1. Turn off "Mow the Grass"
   On your handymen, there are options for "Sweep Footpaths", "Water Gardens", "Empty Litter Bins", and "Mow Grass".
   
   If you do not un-check "Mow Grass", your handyman will spend most of his time cutting the grass, neglecting the paths and trash cans.
   
2. Set a "Patrol Area" for each Handyman
   If you do not set a specific area for a handyman to work, he will wander all over the place, again neglecting dirty paths and full trash cans, unless he just happens to stumble across it. Define where you want him to work.
   
   I suggest no more than about 6 "squares", depending on how complicated your paths are.
3. Make Sure All Paths are Covered by a Handyman
   If you notice in this particular screen shot
   
   the bench and trash can at the bottom of the screen are not covered by the handyman's "Patrol Area". Therefore, he will NOT sweep that path, and he will NOT empty that trash can, even if his area is right next to that. So either extend his patrol path or hire another handyman.
   
   
   Note: This is sometimes hard to see in parks with a lot of scenery, a lot of rides, a lot of people, or all three. (See this screen shot, for example.)
   
   
   The best way around this is to make Rides and Scenery "See Through" (an option under the "View Options" menu) and make people invisible.
   
   Then you can more easily see what paths are handled and which ones aren't, and you can also more easily see which paths are "dirty" and which ones aren't.
4. Be Careful when Using Multiple Paths
   Take a look at this picture:
   
   Notice the raised path on the left. Most of it falls within Handyman1's Patrol Area. However, he will NEVER clean it! Why? He can't get to it! The piece that connects it to the rest of his area is patrolled by Handyman2. And Handyman2 will not climb up onto that path because his patrol doesn't extend that far. So what can you do?
   1. Extend Handyman1's Patrol to include that piece.
      
      Be careful here, though. He may get tied up on either the top part or bottom part, and neither may stay as clean as you want it to.
   2. Hire another Handyman to patrol the upper level.
      
      As you can see, Handyman3 will get the upper level, Handyman1 will stay where he is, and Handyman2 will cover the connecting piece.
   3. Redesign your path.
      Just by moving your path over one square, it is no longer in Handyman1's Patrol Area.
      
      
      Of course, you will need to hire another handyman to handle that new path.
      
5. Hire an Extra Handyman
   Yes, this will cost you some extra money, but it'll be worth it. Once your park gets a little bit bigger, with more people, and more messes to clean up, hire a new handyman, and DON'T assign him a patrol area. (Make sure you turn off "Mow the Grass", though!) Have him wander the park, cleaning up miscellaneous places, and be ready to pick him up and put him where you need him if you find a trouble-spot.

All Handymen can do is clean up after a mess has happened. Here are some ways to help prevent messes in the first place.

1. Put Benches and Trash Cans Near Food Stalls
   Food and drinks causes trash (burger wrappers, empty cups, etc.) and people will need places to throw that trash away. It's a good idea to have benches near the food places, so people can eat near there and not have to go too far. And then, of course, you'll need trash cans near there as well, so they can throw away their stuff. Otherwise, they'll leave a mess.
   
   
   
2. Put Benches Near Ride Exits
   This is especially true for rides with a high intensity or high nausea level. Some people need to sit down after riding a rough ride, or else they will get sick.
   
   
   If they don't get sick, they don't mess up the sidewalk. If they don't mess up the sidewalk, it makes the handyman's job easier.
   
3. Put Bathrooms Near Ride Exits
   This is similar to the statement above. I'm not 100% sure this helps, but it certainly doesn't hurt anything.
   

I hope this information was helpful! If you have any comments, suggestions, or anything you would like to add, please let me know.