Well, at work we are currently selling pool chemicals so here's some tips.

To keep costs of filters and chemicals down, cover your pool when you are not using it. This will keep more chlorine in your water as the sun evaporates it and rain will delute it. Also rain will screw up the chemical balance of the other things like alkilenity and calcium.

Change your filter every 2-3 weeks, every week if you use it a great deal.

ALWAYS TEST YOUR POOL BEFORE YOU SWIM! I had a customer, idiot that her husband was, who accidentally put 3x the amount of chlorine needed and then let their kids swim in it. Both children got chemical burns and who knows what else wrong with them.

If you just do regular maintience you won't have large bills cause your pumps and such won't have to work as hard.