Having owned our home and installed an outdoor fountain with 3 tiers, I believe I can help answer your question. In short, there's no quick fix or easy answer to what comes down to grunt maintenance. Yes, birds will deposit remnants into your fountain and grass clippings, leaves and other detritus will make its way into your bowls and likely clog your filter unless you are dilligent about keeping it clean.
As I live in the Midwest, I get about 7 months of pleasure from ours and then have to winterize it. If you live in an area sans freezing weather you'll just have to clean and drain yearly.
My recommendation: Start with clean bowls and a clean filter every year. No instruction guide needed, but a scrub brush, some elbow grease and maybe some soft scrub are needed to make it look good. Of course, you should do this with a dry fountain upon yearly start up so that your pump filter is clean and free of muck. If you are squeamish about going in with bare hands or have any open cuts, use some form of hand protection or non-alleregic waterproofgloves. Or, simply wash your hands REALLY REALLY well after any cleaning or contact with dirty water.
Once the bowls and pump/filter is clean and dry, inspect for cracks and use appropriate caulk, sealant paint or other coating to prevent further deterioration. Note: our fountain has lasted 16 years with proper maintenance and winterization. After application and drying, refill with clean water and add a cup full of vinegar. This is safe for birds, grass and plants when you spill over or drain your fountain. Because of wind, droppings, and general deposits into your fountain, you'll want to clear out the leaves and such on a weekly basis. I use a small fish net to grab leaves and such or my hands if I'm just casually walking by a see things floating. It's easier to catch these when they're fresh than when decayed and mucky.
When you refill with water because of evaporation, add a bit more vinegar. This also keeps the bowls themselves cleaner and easier to scrub if needed. Unfortunately, there's no substitute for this type of maintenance and I've gotten it down to about 10-15 minutes a week. Although, during hot summer months, daily additions of water are necessary.
Winterization (if needed): drain water out of all tiers. I use a shop vac and simply empty the water onto my grass. Note: if you do "shock" your fountain with chlorine you may burn your grass or plants depending upon the concentration. Once drained and dried completely, I put burlap or junky towels inside each bowl and then cover with a BIG tarp or custom cover which is tied down on the bottom and ready for those winter gusts, snow and ice. In the spring, I begin all over again and enjoy the sounds of my water and sights of birds enjoying their baths and drinks.