First of all try to build up your Urdu vocabulary. So try to write small Urdu words in Urdu, instead of using Roman Urdu. Also search to find good Urdu friends from the plate form of Language Exchange of italki.com. Read simple Urdu story books & also listen to Urdu News on Radio & TV. Urdu News from BBC is also very helpful for you, to recognise Urdu words & sentences. In India, you will find good Urdu speaking friends,from UP try to make friendship, with them they can help you in good Urdu speaking practice. For more situation you may contact me, you will always find me to help you from the plate form of italki.com.

Find someone to practice with, and learn the basics. Good luck.

use youtube .. it helps

To learn any language you have to learn it through its grammar. But if you are wishing to learn slang language then live with the speakers of that language and you will be able to throw the words out of your mouth after some months in sha Allah. But if you know hindi which I think is very similar to urdu in terms of grammar then you only have to learn vocabulary as bro javaid azim said. Best of luck!

if you know Arabic then it would be too easy to learn urdu as both languages are very similar. and if u dont know arabic, then i reecommend u to make friends that speak urdu and read urdu texts more and more. practice it daily.