Of the last four bikes I've owned, the two that were the "bad buys" were when I went into a shop and let them sell me a bike. In both cases I got what they had, and was talked into accepting a bike that just didn't fit. In both cases the shop was large & well known, and in both cases I was pretty excited about buying a bike and not very patient 8-)

The two good bikes were the result of buying a used bike (was mostly an accident) and my recent LHT which was thoroughly researched, and then test ridden in multiple frame sizes at a dealer who was enthusiastic for me to have the right size and made a point to stock them.

So, my advice would be to make sure that whoever you work with while shopping for a new bike has the bike in multiple sizes, and make a point to ride bikes that you suspect won't fit so that you KNOW what a poorly fitting bike feels like. Particularly if you haven't ridden in a while. I'm convinced that there's people who'd rather talk you into a frame that doesn't fit than risk adding inventory by ordering the right size. In some cases (like the LHT) the sizes are close enough that the differences are subtle, but become important over time. Knowledge (from test rides) and patience on your part are your best allies.