Johhny
Best advice I can give is to chose the one you fancy and give them a call either on the phone before you go, or on the correct VHF channel as you approach to make sure they have room.
Have a pen and paper handy to jot down the berth No and which side you want your fenders on.
A search on the internet gives you info and maps/charts with more info.
Yarmouth is nice.
Call them up , and as you approach a small boat arrives to guide you in.
During the week their prices are reduced.
But its only a small place.
We prefer East Cowes marina
again call them for the info
The marina is well kept and nice, free wifi and internet cafe in the office
Nice Pub just outside
and a short walk to the free chain ferry to west cowes
If in doubt call the marina/harbour office and ask
We do not bite