You're right - 3rd gear was your mistake.
In fact, it is best to always be gearing down as you're slowing down so you are always in the right gear and have power available in case you need it. Plus blipping the throttle is fun and sounds cool. I even do it in my car.
An exercise I used to do was to zig-zag through parking spaces in an empty lot - basically a series of tight U-turns. Keep increasing your speed as you get comfortable and you'll be scraping pegs in no time.
Try slipping the clutch and dragging the rear brake instead of disengaging the clutch entirely.
If you were still in 3rd you would have known it if you were slipping the clutch, instead of finding out when you re-engaged it.
OP the above advice is very sound, it's all you need to make a good turn in addition to watching your tachometer, if you still are not sure which gear you are in after shifting down too fast, watching your tacho meter will let you know if you are in too high of a gear still or not or in the right one, and always try to smooth the clutch out each time you shift down so its somewhat engaged, if you had it all the way pressed it means you need more practice knowing what gear you're in how to use the braking with the downshifting so thats never an issue, every bike has the average rpm range, i think on the 250 its around the 4ooorpms, which is enough that its not high reving and not low enough to slow the bike down too fast and enough not to skid or make the engine scream, bigger bikes have a different range.
Also when you make U-turns you lean the opposite direction of the lean of your bike to balance it, its the opposite of what you would do when the bike is at high speed turn.
practice in a parking lot with cones or make your own cones out of empty can's, and use the motorcycle hand book for the slalom M1 bike test as a starting point, practice doing a slalom, once you get good at that, do figure 8's, in both directions, and trust me you will become and ACE in tight cornering and U-turns with good practice on that.
And from there on you can create your own diagrams with cones to practice even harder and slower obsticles. practice it once in a while in a parking lot to keep the precision, since riding is seasonal here.
Good luck and yea falling is all part of learning and riding, i've stalled infront of people too, not because i was in the wrong gear or what have you, my clutching is so precise, that my clutching and throttle became slithly off when my clutch wore off a bit more at that point in time, but then i got used to the newer clutch position, this happens because i tend to use my clutches till when they are at 5% life left, since i have to change it myself.lol
