RE of PCR Fragment - (Mar/17/2008 )

Hi there, I am trying to digest a PCR frament with two different RE NdeI and XhoI in sites I have added to the end. Does anyone know how many extra nucleoties are requirewd for these two enzymes to cu properly?. Where can I find the same information for all the enzymes? I have beedn trying to do a ligation for a long long times without sucess and I be,ive the reason is becouse I only added 6 nucletides and I need more, at least for XhoI. Thank you

thanks. Tom