It's a very, very long time since I was involved in this but we used nutrient agar plates seeded with sufficient of the host organism to produce a thin but continuous film of bacteria when incubated.  If you then flood each plate with aliquots of successive 10-fold dilutions of your phage suspension (as many replicates as you like) one of them should have a countable number of plaques from which you can estimate then number of phage in your source suspension. 

If you need to do this repeatedly it may be better to cut wells in the agar and fill each with an aliquot of successive 2-fold dilutions of phage suspension.  Then you can plot the diameter of the bacteria-free zone against the (log of?) the dilution factor and estimate the zero point.  Preferably you will have a standard suspension, against which you can compare your results.

When you say that plaques are not forming - please provide a description of what you have tried already so that we can review it. The basic procedure for counting phage plaques is well described in countless papers and laboratory manuals. 

I'm talking about experiments carried out in the early 1960s, when  transduction was one technique for gene mapping!  I'd be horrified if there were not better ways of counting phages now.

Stephen - not really. Except that now you can do spot titers with a micro pipet and 10l spots. So that is a bit faster. But I also did tens of thousands of phage titers (in the 70s)

I must admit that we didn't actually use the wells for phages, we used them for estimating antibiotic concentrations.   To be truthful, I'm not sure it would work well for phages but it might be worth a try.  We compared zones of inhibition graphically with those produced by solutions of known concentration.  For phages you'd need enough phage to produce a measurable death zone but it wouldn't be the same as simple diffusion.