Would endorse most of the tips given . If the river you are fishing is match fished , pay a visit at the weigh ins , see if barbel have been caught or anglers reporting being broken by large fish .As Mr Craine suggests visiting a river when the water is very low can reveal likely looking spots . I am not a fan of heavy groundbaiting / chucking in lots of freebies , you are there to get the barbel to take your hookbait not fill em up with free food . IF Barbel are there and conditions are right they will take most hookbaits , very few Barbel can resist a large lump of spam . Also don't be in too much of a rush , give a swim a couple of hours , Barbel do patrol around, I have lost count of the times I have left a big lump of spam on the bottom for 2 maybe 3 hours , absolutely nothing then bang , fish on, often followed by others . Good luck .