I also keep a diary and highly recommend it. My (mental) checklist looks something like this:
Daily:
- count the fish, look for any signs of stress/disease
- feed the fish once
- make sure all the equipment is running properly
- check the temperature
- watch the fish for at least half an hour - this lets me get a feel for their 'normal' behaviour so it's easy to tell when anything's off.
Every 48 hours
- test NO3, Fe and PO4, fertilize as necessary
- check the pH & KH (still need to do this to monitor DIY CO2 output, will be able to test less frequently once I learn exactly how long my mix lasts)
Weekly
- change 50% of the water (sometimes do this 2x weekly - never less than once weekly)
- prune plants
- check CO2 (usually have to replace once a week)
- rinse out the filter sponges in a bucket of tank water, clean uptake tubes of HOBs
- clean the cover glasses with vinegar
- clean any algae off front glass
- fast the fish for one day a week
- test pH, KH, PO4, Fe, NO3
Monthly
- gently disturb substrate in planted tank so it doesn't compact and become stagnant
- filter with diatom filter to polish water & remove any parasites/algae
Every 6 months
- replace old food
- replace old fluorescent bulbs
Every year
- replace CF bulbs