Where you work has large impact on how you work, but when you're working in a cluttered or messy environment, it can cause you to be distracted and it will affect and impact your work productivity and most commonly in a negative way.
The easiest way to get started in minimizing your desk or workplace clutter is to start with a purge. The duration of the purge period will be determined by your efficiency in organizing everything and how chaotic everything was to begin with. When starting, create three catch all spaces; one for important documents, one for things (umbrella, travel mug etc.) and then one for trash. After organizing everything into their specific catch all locations, you can start on the physical space.
Many find that the two-tray system works well. Have two trays on your desk for important documents, one for new items to deal with that haven't been reviewed and the other for items that have been reviewed that still need to be dealt with. Once handled or completed, the documents are to file away in a file cabinet, shredded or tossed depending on the specific circumstances of that document.
As tempting as it can be to want to leave your cute pencil cup or paper clip holder on your desk, these items are better stored in drawers, shelves and storage boxes. The less you have on your desk, the better you'll be and the less distracted you will become at work. Plus, when these clutter-causing items are out of site, you are less likely to need them as often and therefore likely decrease the document hoarding.
The last thing to help keep you organized is getting a bigger trashcan and the reason is simply psychology. You're more likely to think about it and actually use it. It's actually a strategic hack, because the trashcan is more prominent and less likely to reach capacity so fast and thus overflow. When one's trash can overflows your office looks messier and you often stop tossing papers in the trash but leaving them on your desk.
There should be a place for everything and everything goes in its place. When you are not thinking about or distracted by the mess or clutter around you, it leaves your mind free to focus at the tasks on hand.