Its one of those methods Ben, that is easier shown and done than explained!
Everyone has their own little ways of doing it, and as long as you are catching fish, non are more right than others.
Personally, I like to be in the water where I can, which in its self brings its own set of problems.
I try to split the run (I prefer to call it a run rather than a swim, because I'm looking to cover a large area) into two of three areas- near bank, middle and far bank.
I try to work each area making sure I've run the bait through any possible fish holding spots, be that depressions, drop offs, crease's, weed beds, rocks, clear patches, over hanging trees/bushes & snags
I try to fish the near side first, just in case I can hook a fish close in. If you just cast out to the far side and happen to hook a fish you've got to bring it back through an area that might be holding more fish, and you've just spooked them.
I cast well up stream and allow the bait to sink as quick as I can. I want it close to the bottom asap so I'm fishing effectively.
I let a bow form downstream, which means the bait should be bouncing in a straight line down the swim.
I then feel the line in my left hand, with the rod pointing down stream so it creates an angle of around 90 degrees from rod top to where the line enters the water.
You should feel the bait tripping bottom, and by holding the line in your left hand (if you are right handed) you can read whats happening to the bait.
Like I said, its much easier to show you than it is to explain in writing (well for me it is anyway).
If you are ever up on the middle Severn, I'd be more than happy to show you how I do it.....
Steve