IGEM:MIT/2005/Anneal

Your annealing temperature is 5 degrees below lowest of the two the melting temperatures of the landing sequence portion of your primers. This step is done for one minute unless special circumstances apply.

(The landing sequence is the portion of the primer that binds to the DNA initiall -- it is only part of the sequence if you are adding on BB ends, for example, or it is the entire primer if you are not adding anything).