hi!
im amplifying a gene of known molecular weight (1.3kb) after designing forward reverse primers.when i run pcr ,im getting d desired band but ofvery weak intensity. besides i can see a very strong band of v low molecular weight in d gel . may be a primer dimer. how do i get the desired band of high intensity as i need to sequence n clone tht fragment . do i need to change the primer concentration or temp of annealing in my pcr?

Try decreasing your annealing temp or increase your Mg-concentration a bit. How big is the low molecular weight strong band? Is it a couple 100 bp or below 100 bp?
How many cycles do you run?