When I was doing this I came with a friend, we ordered a coffee, stayed for a cigarette and were commenting some live match on TV loudly. The point is indeed to make bookmakers think you are an ordinary person, stupid and naive and hoping for some big win, which is why I was also making another "mug" bet accumulator with many legs and low stake. This is only useful assuming you are laying your bet at exchange, if you need to visit more bookmakers quickly then no time for coffee