Plaque Assay Protocol for Pseudoalteromonas
First, autoclave the top agar to melt it.
While the autoclave is running, let your bottom agar plates warm to room temperature and label them and make whatever dilutions of your phages you plan to plate.
Note:  it is wise to plate one dilution higher and one dilution lower than what you calculated as optimal. 
Aliquot the agar into tubes and place in 40°C water bath.
Pipet 100 μl of your phage sample onto the plate.   
Remove the agar tube from the water bath and add the host to it using a 1 ml or 5 ml pipettor. 
Add 3.5 ml of the agar/host mixture to each plate.
Swirl the plate to spread the agar making sure it covers the whole plate.
Leave the plates on the bench overnight. 
Count or pick plaques the next day
