please help me-basic information about site-directed mutagenesis PCR

[trypsin]

I have to change a codon in my plasmid vector. It should be changed by site-directed mutagenesis.
Now I know that i made any mistakes. I have no idea which kind of parameters and substances are important to get a good result.

Somebody told me I must use a primer which has minimum 30-35 bp and a GC-end. She told me the annealing temperature should always be 55°C independent of the primer length (what i don't understand). I have two protocols: the first describes the use of only one primer (forward primer with the changed na) the second describes the use of two primers (forward and reverse primer). What is the right or better protocol?
I use the pfu high fidelity polymerase at 68°C. Is this the right/optimal temperature? Or should i use another polymerase? How many cycles should be do? I know that 35 cycles are too much.
I would be very happy if someone could get me some information or tips.
thank you.
trypsin

[kmunson779]

I follow the guidelines in the Stratagene QuikChange [Only registered users see links. ], except I usually put my mutation at the 5' ends of my primers rather than in the middle. Stratagene also has a free [Only registered users see links. ] to design primers.