The most common approach is to take a field sample, add water, vortex for 30 mins, centrifuge large particles down and then pass the supernatant through an appropriate filter that will allow the phage particles though but not bacteria. You then do a PEG precipitation and resuspension step to concentrate before applying this solution to lawns of the desired bacteria and looking for impaired growth or lysis.

Switch to SM buffer instead of TMG buffer or any other buffer.

Decrease the agar concentration to 0.4 to 0.6 % in soft agar.

Use BHI agar for phage isolation.