One more thing. Try blipping the throttle a little as you press on the shifter. That can sometimes help the gears mesh a little better. If you are sure you are doing it right, and it still doesn't work properly, you have mechanical problems. To check for a dragging clutch, put the bike in first, keep the clutch pulled in, and give it a little throttle. If it creeps forward, you have a dragging clutch.
2016 Rebel, 2013 Royal Enfield B5, 2009 Genuine Stella, 2006 H-D Sportster 1200, 2006 Vespa GT200, 2001 Yamaha XT225
"I refuse to believe in a risk free society where the thrill of living is traded for the safety of existence." — Nick Ienatsch