Here is a handy spreadsheet that can be used to calculate your training zones based on your max and resting heart rates (should be averaged over a couple of days):
http://www.brianmac.co.uk/excel/hrmzones.xls
And here is some more information about how to use those zones.
http://www.brianmac.co.uk/hrm1.htm
Keep in mind that these values (MHR & lactic threshold in particular) are based on population norms, and that as you train you will get a better idea of what your personal MHR & LT are.