Seasonal pitch advice please?

I wonder if anyone could offer some advice about seasonal pitches? We are about the buy our first caravan and the idea of putting it on a seasonal pitch would be very convenient for us whilst we get into the swing of things having no real experience. A site in North Wales would be ideal as we don't want to travel too far having two toddlers. I seem to be struggling on the internet for info on who offers this service? When i have found the odd site that offers this there are no prices? Is this because price is negotiable? I feel nervous about calling as i don't know what questions to be asking? How hard are these pitches to come by, are there waiting lists for certain sites? Any advice at all about what to look for, what to ask, where to look would be great. Many thanks in advance!