>1.How can I remove (or reduce) the primer dimer in PCR reaction
> how about increase annealing Temp ? or lowering Ma2+ conc.
Of course, you can try this, The best way is to design good primer which
difficult to form dimer
>>2.After 38 cycles, a faint signal was obtained. Can I increase
> cycle number, or template DNA or even dNTP content
> TO further INCREASE THE SIGNAL I WANT ??
Too many cycles, why not cut the band and do the second again
>>3.What's the best methods to elute out the PCR product with
> high yields and low DNase contaminated. ANY kits suggested ?
Promega wizard and Qiagen PCR product purfication kit work well for me