To have a better command of the English language, all I can say
is: immerse yourself in it. Read more English, think more English,
and speak more English.
Do small changes in your everyday life to help you work on
improving your English. Write proper sentences in your SMSes and
your MSN messages, for instance. Instead of writing 'Hey, wan 2 go
4 dinner tonite?' in your SMS, type out a proper 'Hey, do you wish
to meet for dinner tonight?' instead.
Otherwise, if writing in SMS lingo becomes second nature to you,
then it's hard to write proper English anymore. My tuition student
has a very, very bad habit of using SMS lingo in his compositions.
I've since warned him to switch to proper sentences in his SMSes,
but he resists doing so.
So for now I'm still heavily penalising him for those mistakes in
his compositions. Don't fall into the same trap as he has.