You want to carry as much momentum as you possibly can, so i would suggest always choosing a higher gear so as not to lose momentum while corning. Also using the clutch and not having power go to the rear wheel will cause you to lose some of your control over the bike, you want power being put on the groud as much as possible so i would suggest not using your clutch before corning unless you are shifting or braking very hard. If you are having to brake hard before a turn then using the clutch will keep you from stalling, but this is not an ideal situation, you perferably want to use the brkaes as little as possible because like i said before momentum is key!
What type of riding are you doing, Motocross or trail? Depending on which one you are doing i might be able to give a few more tips!