Keep it simple, don't get sucked in by overly complicated rigs. Concentrate on learning where the fish are, location is 80% of the battle. Look for snags like trees fallen in the river or overhanging trees, creases between faster water and deeper, slower sections and weed beds.
A simple running rig with a few different baits to try, maybe halibut pellets, luncheon meat and a natural bait like maggots or lob worms.
Don't be worried about moving pegs, in fact mobility is a bonus. If you're only fishing for a day session you will have more success by finding the fish rather than waiting for them to find you. Give each swim 20 minutes or so, if there's no action then move on.
I often use small PVA bags made up before I set out, put a selection of your hookbaits for the day inside (not so easy with maggots & worms but ok for pellets). These will trickle down stream from your hookbait into the snag or under the tree etc...
Make sure if you're starting to fish for them in the summer that you don't keep them out of the water for long and when returning them be prepared to support them in the flow until they are fully recovered. Barbel are particularly succeptable to exhaustion in warm weather when the water's oxygen content is lower. They can seem ok to go and then turn belly up out of reach in the middle of the river.
Hope that's helpful.
