You can contribute whatever the annual maximum is (currently $5500 – but rumours suggest that if the Federal Government of Canada balances their books, it could go up to $10000). Rich people would be going bananas.
What about withdrawals?
Say you have $10,000 in it and want to withdraw $2500 in 2013. You cannot just put it right back in there. You have to wait until the following year to be able to contribute that $2500 back in, PLUS you can contribute the new 2014 allotment of another $5500.
It goes like this - If you withdraw in one year, you can only put that amount withdrawn back in the following year.
Now without further ado (whatever that is), what not to do with your TFSA.