I bought my first house in Florida in Oct 09 and wish to make it my primary residence. I have spent 6 months out of the year commuting back and forth in both 09 and 10. I still work full time in NY and stay at my parents home but fly back frequently. I have always filed taxes as a NY resident. Can I switch to a Florida residency and declare taxes in NY? How does this residency/taxes thing work?

The way it works is you have to pay NY state income tax on your NY source of income - meaning your wages from your job - even if you live out of state. If you work in NY but reside in FL you would file a non-resident NY State tax return. The tax rates are the same as for residents, so there's not much point in trying to convince the NY tax authorities that you are a FL resident unless you have other sources of income that you want to shield from NY taxes (investment income, for example), or unless your parents residence is in NY City or Yonkers and you are trying to avoid paying the NYC/Yonkers residency tax. But to claim FL as your primary residence you must be able to demonstrate that you spend at least 50% of your time there. I suspect that if you have a full time job in NY this woud be difficult to show.