Hi Andy
The best way to find marks worth fishing is to look at your admiralty chart of the area and look for features. Things such as banks, rough ground, holes, or ledges can all be good fish holding areas.
If you are fishing inshore you might like to try Old Harry to Ballard for Bream or Poole Patch theses popular areas are plainly shown on the chart.
An easy way to find marks is to join a club that specializes in boat fishing if you can find one . Over a period of time you would pick up from other members where they fish and what can be expected in a given area. If your interested in this club then send an email to martin.burt1@ntlworld.com and you will receive a new member pack by return which might help you decide wether pbsbac is worth joining.
Regards
Martin