I worked in the office for many years.
Worth remembering that some records will be essentially worthless to them, even though they don't refuse anything. So they're more interested in the good stuff. I'd say self-selection is the key. Prune out the rubbish, if you can. Consider giving some stuff to charity shops. Go in there with a high average quality of record, and it helps the guy behind the counter.
Also, make sure the records you've got are suited, area-wise, to the shop you're going into. The soul shop don't want to wade through lots of rawwwwk.
Most other protocols of how to deal with them can be determined by thinking how much work you're gonna cause the guy behind the counter. So, don't present them with an enormous list of stuff and ask them to present an exact price. But maybe think of doing a list of 100 odd of the best records and ask if they're interested. They won't refuse anything, but you might be able to get a sense of if they think they'd be good purchases for the shop.
Great stuff > eBay
Decent stuff > MVE
Standard stuff > charity shops
Remember that, in any given case, you might not get much money, so don't spend 50 quid on a taxi down there.
Also remember that you will be able to cut out the middle man (which is what MVE/RTE is) by selling them on eBay. If you've got the time.