OK so i played badminton today after school...a lot of clears i do go OUT(past the back line) even when i dont hit hard...and i'm wondering why and how to prevent this....also, i did some backhard returns of drives, and they went out(past the back line)...also i returned a smash by just BLOCKING it with my racquet, didnt even swing...and it still went out(past the back line AGAIN)....i'm using plastic shuttles(carlton to be exact), with an iso300 strung at 24lb cross 22 main.
how can i prevent this from happening anymore? Any sort of technique i could improve on? or could it be my string tension?(i have never had this problem before when my iso300 was strung at about 18lb).

it's called you have no feel. you're not use to that tension yet. it'll take some time, and practising before you get use to that tension. it's a pretty huge jump from 18 to 24. try 18 to 35 that's very interesting :)

Shaun, do you normally use Yonex nylon shuttles? I have found Carltons to be a slight bit faster than Mavis 300 shuttles, which might account for some of your problems. Also, check the condition and shape of the shuttles - if they are a bit crushed, you may want to pull the edges outward to slow down the shuttle.

On your clears, try hitting a little bit higher so gravity will take some of the speed off your shots. Of course, you will have to maintain a reasonable balance between pace and height, or your opponents will be able to get under your clears too easily and smash.

hmm thanks guys...i guess i just need to get used to the string tension and hit higher "] (but sometimes its too high already).
i am used yo mavis300 shuttles...hate that carlton stuff...

Carltons don't fly as well as mavis 300. Most school sanctioned tournaments are using mavis 300 so it's a good idea to use them.

Yup, hit it higher.
And check your position when you hit it out. Are standing in the back two tram lines?
Do you know sometimes it is a tactic to hit a short clear so that your opponent may hit the shuttle out on his clear?

thats one good tactic cheung "] never seen it done before..
but ya, i was clearing from about mid court..

Test the birds, if you're not sure if its the racquet or birds, stand at back tram lines and underhand clear to other side. If you hit out of court on otherside its probably the bird at fault (broken/folded).

If its not the bird, hit higher trajectory as stated above, vertically falling birds harder to smash as well.

agreed. Especially plastic shuttles usually come in three speed, slow, medium and fast as compare the feather which had a lot more speed selection. Check the plastic bird before you start the game. In calgary, we use slow plastic but it is still not slow enough. We have the flare the plastic skirt more to slow it down.