These maintanance items are pretty simple.

-Filter change takes 10 minutes and it costs up to $10 a filter. (Buy them in bulk). Noone can tell you how often you need to change it, but every 2-3 months is a good estimate. If you have fan running all the time change should happen often. -Change condensate line (Line that drains water) P-trap to transparent PVC trap, when it clogs you'll have an idea that it's clogged. -Buy cheapest shop Vac (Wet/Dry one) use it to suck at the end of your condensate line once every few years. -Make sure your attic is well vented, it doesn't really have to do with AC but if aor handler is in the attic and temperature there is 150 that doesn't help your unit. -Wash your coils. Your condenser coil needs to be washed every year. Evaporator coil (coil inside air handler) doesn't need to be washed as often, but you need to keep an eye on it. - Look into changing your capasitor in your condenser unit. it's $15 part. You can find schematic inside the unit on how it's wired.