I ran out of gas twice on my DRZ, both times on hilly roads with no traffic around, before I figured out the fuel range. I ran out of gas 3 times on my GS500, once on an expressway, twice on the freeway, after some carburator work was done that worsened my gas mileage significnatly.
I used to wonder what it felt like to run dry. You’d first notice a slight stumble, a slight loss of power, then it would run rough, and the engine would die in about 15 seconds or so (a rough estimate, not exact). That’s enough time for you to react, to pull over, when the traffic’s light, but it could be hairy in heavy traffic. Some riders are able to switch to reserve on the fly without the engine dying or stopping the bike. I haven’t practiced reaching for the petcock without looking and switching to reserve while the bike’s moving, so I just pulled over, stopped with the engine dead, then switched to reserve and restarted the bike. If it really ran dry and the bike would not start on reserve, switch the petcock to “prime” to allow the gas to flow into the carburator for a couple of seconds, start the bike, then switch to reserve.
Often there’s still a rediculous amount of gas left in the tank (like a gallon) when you hit reserve, so going another 20-30 miles in reserve is usually no problem. Of course, each bike is different.