so what you do is go in 2nd or third gear then rev it then pull clutch in ( optional you can pull front brake in to preload the bike) then just drop your clutch and you should come up. when you get in the wheelie postion theres a thing called balence point and thats where you feel comfortable in your wheelie. and to keep it up use your throttle and rear brake
That's nothing for a TTR 125 you should be able to ride wheelies for Miles with that thing they've got real good balance and a pretty predictable power range