We currently set aside $106 per month for property taxes. This can be tricky to estimate right, because it can change every year. This year, our annual taxes were $1,270; last year they were $1,416. The year before that, they were different still.
We generally use last year's tax amount as an estimate for this year. So we'll set our budget in November and then adjust it when we actually get the bill mid-spring (Februaryish, with half due in April and half due in October).
There isn't generally a whole lot that can be done to lower property taxes. We could rent instead of own, but then we'd be paying more for rent than mortgage + taxes. There are some programs for mitigating taxes for people below a certain income threshold (not sure what it is, but it's a REALLY low income level). You can ask the gov't (the county, in our case) to reassess your property. We did this last year, because we thought our house was overvalued (and hence over-taxed); the county sent a couple people out to actually look at the condition of the house, and they told us they may or may not adjust it for us, but it looked promising. The new assessment came and our taxes were almost $150 lower. That saved us a little over $12/month this year.
A couple other notes which may or may not apply:
Pay cash or check. Our county is, for whatever reason, prohibited from absorbing the cost of processing credit/debit charges. If I pay with my debit card, I pay a $2 fee; and if I pay with my credit card, I pay 3%.
Pay on time, of course. Our tax due dates are always the last day of the month (April 30th and October 31st). I replenish the budget on the 1st of the month-- that means that I have the whole amount of money already in my account and budget so I have the whole month to find a convenient day to include "Pay The Taxes" in my errand list.
Pay in person. This will save you the $0.49 of the stamp. Just make sure you combine this errand with other errands that you also need to run-- for us, the County office is only two blocks from our bank, so it's an easy one for us to combine.